Energy storage device

Abstract

Energy storage device comprising: a first electrode sheet; and a second electrode sheet stacked on the first electrode sheet, wherein a separator is disposed between the first electrode sheet and the second electrode sheet, and having a polarity different from a polarity of the first electrode sheet, wherein the first electrode sheet comprises: a metal foil having an edge portion extending linearly in a first direction and a first tab extending 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 insulation layer formed on the surface of the metal foil, wherein a portion extending along the edge portion and the first tab of the metal foil are formed into an active material non-formation portion in which the active material layer is not formed, and wherein the insulating layer is formed on the active material non-formation portion.

Description

Technical area

[0001] The present invention relates to an energy storage device having a positive electrode sheet and a negative electrode sheet stacked together with a separator disposed therebetween. State of the art

[0002] In an energy storage device such as a lithium-ion battery, there may be a case where the energy storage device uses an electrode assembly comprising a positive electrode sheet and a negative electrode sheet stacked alternately with a separator disposed between them. Generally, the positive electrode sheet and the negative electrode sheet are formed by coating an active material layer on both surfaces of a metal foil.

[0003] As disclosed in Patent Document 1, there may be a case where tabs are formed on a positive electrode sheet and a negative electrode sheet of an energy storage device such that each of the tabs protrudes outward in a width direction from a straight edge portion of the sheet on one side in the width direction. At least a portion of the tab is formed as an active material non-formation portion in which no active material layer is formed, and the active material non-formation portion is electrically connected to an external terminal via a current collector.

[0004] In this type of energy storage device, there may be a case where, on the positive electrode sheet, an active material non-formation portion is formed not only on the tab, but also on a portion along an edge portion of the positive electrode sheet from which the tab protrudes. There may also be a case where the active material non-formation portion formed along the edge portion of the positive electrode sheet in this way is arranged to face and oppose an active material layer of the negative electrode sheet with a separator interposed therebetween. State-of-the-art document

[0005] Patent Document 1: Japanese Patent No. 5354042 Summary of the inventionProblems to be solved by the invention

[0006] In the above-described energy storage device in which the active material non-formation portion formed along the edge portion of the positive electrode sheet on a tab side is arranged to face and oppose the negative active material layer with the separator interposed therebetween, there is a possibility that when a state is brought about in which a positive active material non-formation portion and a negative active material layer directly oppose and face each other due to a cause such as positional displacement, shrinkage, or breakage of the separator, a short circuit occurs between the positive active material non-formation portion and the negative active material layer.

[0007] The present invention has been made in view of the foregoing, and an object of the present invention is to suppress the occurrence of a short circuit in an active material non-formation portion in a power storage device including the active material non-formation portion formed along an edge portion of an electrode sheet on a tab side. Means to solve the problems

[0008] An energy storage device according to the present invention comprises: a first electrode sheet; and a second electrode sheet stacked on the first electrode sheet, wherein a separator is disposed between the first electrode sheet and the second electrode sheet and has a polarity different from a polarity of the first electrode sheet, wherein the first electrode sheet comprises: a metal foil having an edge portion extending linearly in a first direction and having a first tab extending from the edge portion in a second direction intersecting with 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, wherein a portion extending along the edge portion and the first tab of the metal foil are formed into an active material non-formation portion in which the active material layer is not formed, and wherein the insulating layer is formed on the active material non-formation portion;

[0009] With such a configuration, even if a state is created where the first electrode sheet and the second electrode sheet directly and oppositely face each other due to positional displacement, shrinkage, breakage, or the like of the separator, the occurrence of a short circuit in the active material non-formation portion of the first electrode sheet can be suppressed. This is because the insulation layer is arranged between the active material non-formation portion of the first electrode sheet and the second electrode sheet.

[0010] In the present invention, it is advantageous that the insulating layer is formed in a region of the active material non-formation portion that includes a proximal portion of the first tab. With such a configuration, it is possible to reinforce the proximal portion of the first tab with the insulating layer while simultaneously suppressing the occurrence of short circuits at the proximal portion of the first tab.

[0011] In the present invention, it is advantageous for the first tab to be rounded at its proximal portion. With such a configuration, stress is distributed across the proximal portion of the first tab, thus increasing the strength of the first tab.

[0012] In a case where the energy storage device according to the present invention further comprises 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 the bent state. In this case, the proximal portion of the first tab, where bending stress is concentrated, is reinforced by the insulation layer, so that the rigidity and durability of the first tab can be improved.

[0013] In the present invention, it is advantageous that a part of the insulating layer formed on a surface of the first tab protrudes from an edge portion of the separator in the second direction. With such a configuration, even if a state is created where the first tab faces the second electrode sheet without the separator intervening due to positional displacement, shrinkage, breakage, or the like of the separator, the occurrence of short circuits in the first tab can be suppressed because the insulating layer is interposed between the metal foil of the first tab and the second electrode sheet.

[0014] In the present invention, it is advantageous that the insulating layer is also formed on an end surface of the metal foil in the active material non-formation portion. With such a configuration, the occurrence of short circuits in the active material non-formation portion of the first electrode sheet can be better suppressed. Furthermore, the end surface of the edge portion of the first electrode sheet is covered by the insulating layer, so that, while suppressing the occurrence of short circuits at the end surface of the edge portion, the edge portion of the first electrode sheet can be easily arranged by arranging the edge portion of the first electrode sheet near the edge portion of the separator located outside the edge portion of the first electrode sheet in the second direction. Accordingly, the first electrode sheet can be expanded in the second direction, so that the battery capacity can be increased.

[0015] In the present invention, in the case where the second electrode sheet has an edge portion extending linearly in the first direction and a second tab extending in the second direction from the edge portion, the first tab and the second tab can protrude to the same side in the second direction while being spaced apart from each other in the first direction. In this case, this type of energy storage device can achieve the above-mentioned advantageous effects.

[0016] In the present invention, in the case where the first electrode sheet has a plurality of first tabs arranged spaced apart from each other in the first direction, and a wound body is formed by winding the first electrode sheet and the second electrode sheet around an axis parallel to the second direction while overlapping the first electrode sheet and the second electrode sheet with the separator interposed therebetween, the wound body may include a first tab bundle formed by stacking the plurality of first tabs. In this case, the rigidity of the proximal portion of the first tab is increased by the insulation layer, so that it is possible to suppress the deflection of the first tab, which deforms in the thickness direction of the first electrode sheet at the time of winding the first electrode sheet.Accordingly, when the plurality of first tabs are overlapped by winding the first electrode sheet, the hooking engagement between the first tabs occurs minimally, so that breakage of each first tab can be suppressed.

[0017] In the present invention, in the case where the winding body includes a pair of flat portions extending in a straight line parallel to each other in a direction in which the axis extends, and a pair of bent portions connecting the pair of flat portions, the first tab bundle can be attached to the flat portion. In this case, this type of energy storage device can achieve the above-mentioned advantageous effects.

[0018] In the case where the energy storage device according to the present invention comprises a layered product formed of a plurality of first electrode sheets and a plurality of second electrode sheets, wherein the first electrode sheet and the second electrode sheet are alternately stacked with the separator disposed between the first electrode sheet and the second electrode sheet, the layered product may include a first tab bundle formed by stacking the first tabs each formed on the plurality of first electrode sheets. In this case, this type of energy storage device can achieve the above-mentioned advantageous effects. Advantages of the invention

[0019] According to the present invention, even when a state is created where the first electrode sheet and the second electrode sheet directly face each other due to positional displacement, shrinkage, breakage, or the like of the separator, the occurrence of a short circuit in the active material non-formation portion of the first electrode sheet can be suppressed. This is because the insulation layer is arranged between the active material non-formation portion of the first electrode sheet and the second electrode sheet. Short description of the drawings Fig. 1 is a perspective view illustrating an energy storage device according to an embodiment of the present invention. Fig. Fig. 2 is a perspective view with a cutaway showing the interior of the energy storage device along a line AA in Fig. 1 shows. Fig. 3 is a perspective view of an electrode assembly of the Fig. 1 shown energy storage device. Fig. 4 is a developed view of the Fig. 3 shown electrode arrangement. Fig. 5 is an enlarged view of Fig. 4, which shows a positive electrode tab of a positive electrode sheet and sections around the positive electrode tab. Fig. Fig. 6 is a cross-sectional view of a first insulating portion of an insulating layer of the positive electrode sheet and portions around the first insulating portion taken along a line BB in Fig. 5 in the longitudinal direction of the positive electrode sheet. Fig. Fig. 7 is a cross-sectional view of a second insulating portion of the insulating layer of the positive electrode sheet and portions around the second insulating portion taken along a line CC in Fig. 5 in the longitudinal direction of the positive electrode sheet. Fig. Fig. 8 is a cross-sectional view of the second insulating portion of the insulating layer of the positive electrode sheet and the portions around the second insulating portion taken along a line DD in Fig. 5 can be viewed in a projection direction of the positive electrode tab. Fig. 9 is an exploded perspective view schematically illustrating an electrode assembly of an energy storage device according to another embodiment of the present invention. Embodiments of the invention

[0020] An embodiment of the present invention will be described below with reference to the accompanying drawings. In this specification, terms including "upper" and "lower" are used to indicate directions, and terms related to these terms and indicating directions are used to indicate directions related to the spatial position of an energy storage device illustrated in the accompanying drawings. These directions do not necessarily correspond to the directions of the energy storage device in an actual use state.

[0021] Fig. Figure 1 shows an energy storage device 1 according to an embodiment of the present invention. The energy storage device 1 is a non-aqueous electrolyte secondary battery, such as a lithium-ion battery. However, the present invention is also applicable to various energy storage devices, including a capacitor in addition to the lithium-ion battery.

[0022] As in Fig. As shown in Figure 1, the energy storage device 1 comprises a housing 2, which, for example, has an approximately rectangular parallelepiped shape. The housing 2 comprises a housing body 3 with an upper surface opening portion, and a lid body 4 that closes the upper surface opening portion of the housing body 3.

[0023] A metal such as aluminum or an aluminum alloy is used as a material for forming the housing body 3. The entire surface of the housing body 3 can be covered, for example, with an insulating layer made of a resin (not shown in the drawing).

[0024] The lid body 4 is formed, for example, from a rectangular metal plate. The lid body 4 is welded to an opening edge portion of the housing body 3. An external terminal 11 of a positive electrode and an external terminal 12 of a negative electrode are attached to a surface of the lid body 4.

[0025] The respective external terminals 11, 12 are each secured to an upper side of the cover body 4 by sealing, e.g., via the upper seals 13. A metal such as aluminum, copper, or nickel is used as the material for forming the external terminals 11, 12.

[0026] A gas vent port 8 for venting a gas generated in the housing body 3 to the outside of the housing 2 and an electrolyte solution filling port (not shown in the drawing) are provided for the cover body 4. The electrolyte solution filling port is closed by an electrolyte solution filling port plug 10.

[0027] As in Fig. 2, at least one electrode assembly 20 (corresponding to the “winding body” in the claims), current collectors 15 electrically connecting the electrode assembly 20 to the external terminals 11, 12 of the positive electrode and the negative electrode, and an electrolyte solution (not shown in the drawing) are stored in the housing 2.

[0028] The Fig. 2 is a positive electrode current collector connected to the positive electrode external terminal 11, the configuration of the positive electrode current collector 15 being described below with reference to Fig. 2, and the illustration and description of a negative electrode current collector connected to the negative electrode external terminal 12 is omitted.

[0029] Although the negative electrode current collector has the same configuration as the positive electrode current collector 15 described below, the negative electrode current collector may have a configuration different from the configuration of the positive electrode current collector 15. Furthermore, the positive electrode current collector 15 and the negative electrode current collector may be made of different materials. Specifically, a metal such as aluminum is used as the material for constituting the positive electrode current collector 15, and a metal such as copper is used as the material for constituting the negative electrode current collector.

[0030] The current collector 15 is fixed to a bottom surface of the lid body 4 by sealing, e.g., via a bottom 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 extending downward while being curved from an edge portion of the first flat plate portion 15a, and a second flat plate portion 15c formed continuously with the first flat plate portion 15a via the connecting portion 15b and disposed oppositely below the first flat plate portion 15a.

[0031] The first flat plate portion 15a is electrically connected to the external terminal 11 via a rivet portion (not shown in the drawing) extending downward from the external terminal 11, for example. The tabs 35 formed on the electrode assembly 20, described later, are joined to a lower surface of the second flat plate portion 15c by, for example, ultrasonic welding. With such a configuration, the external terminal 11 is electrically connected to the electrode assembly 20.

[0032] Also with regard to Fig. 3 and Fig. 4, the electrode assembly 20 is configured such that a positive electrode sheet 21 (corresponding to "first electrode sheet" in the claims), a negative electrode sheet 22 (corresponding to "second electrode sheet" in the claims), and two separators 23, 23, 23, each formed of a microporous resin sheet, each having an elongated tab shape with a fixed width, overlap each other, and are wound into an approximately elongated circular shape with a high degree of flatness. Both of the two separators 23, 23 are arranged between a layer of the positive electrode sheet 21 and a layer of the negative electrode sheet 22, which is arranged adjacent to a layer of the positive electrode sheet 21. The separators 23, 23 are larger than the positive electrode sheet 21 and the negative electrode sheet 22. In such a configuration, an outermost layer of the electrode assembly 20 is formed from the two separators 23.

[0033] An axis of the winding (winding axis) of the positive electrode sheet 21, the negative electrode sheet 22 and the two separators 23, 23 is represented by the symbol X in Fig. 3 conceptually characterized. The electrode assembly 20 is mounted inside the housing body 3 in a position in which the winding axis X extends substantially in a direction in which a lower wall section and the Fig. 1 shown upper surface opening portion of the case body 3 facing each other (in a vertical direction in Fig. 1).

[0034] As in Fig. As shown in Figure 3, the respective end portions of the electrode assembly 20 in a direction in which the winding axis X extends form end surface portions 20a, 20b, on which edge portions of the positive electrode sheet 21 in a width direction (transverse direction), edge portions of the negative electrode sheet 22 in a width direction (transverse direction), and edge portions of the separators 23, 23 in a width direction (transverse direction) are arranged. The electrode assembly 20 includes: a pair of flat portions 20c, 20c arranged to face each other with the winding axis X therebetween and extending straight parallel to each other in a direction in which the winding axis X extends; and a pair of curved portions 20d, 20d, 20d extending in a semicircular curved manner in a direction in which the winding axis X extends and connecting the pair of flat portions 20c, 20c to each other.

[0035] The flat portion 20c is a portion that extends straight in design. In a state where the electrode assembly 20 is actually stored in the housing 2, the flat portion 20c is not always arranged completely straight, and there may be a case where the flat portion 20c is arranged in a curved manner, although the flat portion 20c may be formed into an approximately linear shape overall.

[0036] As in Fig. 3 and Fig. 4, the positive electrode sheet 21 includes: a strip-shaped positive electrode metal foil 24; and positive active material layers 25 formed on both surfaces of the positive electrode metal foil 24, respectively. Edge portions on both sides in the width direction (transverse direction) of the positive electrode metal foil 24 are formed to extend linearly in a longitudinal direction of the positive electrode metal foil 24. On one side in the width direction of the positive electrode metal foil 24 (a bottom side in Fig. 3 and Fig. 4), the positive active material layer 25 is formed so as to reach the edge portion of the positive electrode metal foil 24. On the edge portion on the other side in the width direction of the positive electrode metal foil 24 (a top side in Fig. 3 and Fig. 4) the positive active material layer 25 is not formed, and a first active material non-formation portion 34 is formed in which the positive electrode metal foil 24 is exposed. The first active material non-formation portion 34 of the positive electrode metal foil 24 is covered by an insulation layer 40 as described (see Fig. 5 to 8). In Fig. 3, the illustration of the insulation layer 40 is omitted.

[0037] Although aluminum is used as the material for forming the positive electrode metal foil 24, a metal other than aluminum may be used. As the positive active material, lithium manganate (LiMn2O4), nickel-cobalt-lithium manganate (LiNi x Co y Mn 1-x-yO2), lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO4), and lithium manganese phosphate (LiMnPO4) can be used, which are materials formed by using substitution additives in these composites or mixtures of these composites. However, other transition metal oxides containing lithium can also be used.

[0038] The negative electrode sheet 22 includes: a strip-shaped negative electrode metal foil 26; and negative active material layers 27, each formed on both surfaces of the negative electrode metal foil 26. Edge portions of the negative electrode metal foil 26 on both sides in the width direction (transverse direction) are formed rectilinearly in the longitudinal direction of the negative electrode metal foil 26. On both sides in the width direction of the negative electrode metal foil 26 (a top side and a bottom side in Fig. 3 and Fig. 4) The negative active material layers 27 are formed to reach the edge portions of the negative electrode metal foil 26. With such a configuration, the respective entire surfaces of the negative electrode metal foil 26 are covered by the negative active material layers 27.

[0039] Although copper is used as the material for forming the negative electrode metal foil 26, a metal other than copper may also be used. For example, graphite is used as the negative active material. However, materials that can include lithium may be used, such as other carbon materials, lithium metal, a lithium alloy, lithium titanate (Li4Ti5O 12 ), silicon, silicon monoxide, or tin, or a mixture of these materials.

[0040] In the following description, a longitudinal direction of the positive electrode sheet 21, a longitudinal direction of the negative electrode sheet 22 and a longitudinal direction of the separator 23 (directions indicated by an arrow P in Fig. 4 to Fig. 8) simply referred to as “longitudinal direction P”, a transverse direction of the positive electrode sheet 21, a transverse direction of the negative electrode sheet 22 and a transverse direction of the separator 23 (a direction indicated by an arrow Q in Fig. 4 to Fig. 8) are simply referred to as “transverse direction Q”, and a thickness direction of the positive electrode sheet 21, a thickness direction of the negative electrode sheet 22 and a thickness direction of the separator 23 (directions indicated by an arrow R in Fig. 5 to Fig. 8) are simply referred to as the “thickness direction R”. The longitudinal direction P corresponds to the “first direction” in the claims. The lateral direction Q corresponds to the “second direction” in the claims and is a width direction parallel to the winding axis X (see Fig. 3) the electrode arrangement 20.

[0041] As in Fig. 4, in the transverse direction Q of the positive electrode sheet 21 and the negative electrode sheet 22, a width of the negative electrode sheet 22 is set larger than a width of the positive electrode sheet 21. The negative electrode sheet 22 protrudes outward from an edge portion of the positive electrode sheet 21 on both sides in the transverse direction Q. A width of the separator 23 is set larger than the width of the negative electrode sheet 22. The separator 23 protrudes outward from an edge portion of the negative electrode sheet 22 on both sides in the transverse direction Q.

[0042] As in Fig. 3 and Fig. 4, on the positive electrode metal foil 24, a plurality of positive electrode tabs 35 (corresponding to the “first tab” in the claims) are formed, which protrude outward in the transverse direction Q from the above-mentioned first active material non-formation portion 34 extending linearly along the edge portion of the positive electrode metal foil 24 on one side (an upper side in Fig. 3 and Fig. 4) extending in the transverse direction Q, formed at intervals in the longitudinal direction P. The first active material non-formation portion 34 and the plurality of positive electrode tabs 35 are formed from a sheet of positive electrode metal foil 24, with the respective positive electrode tabs 35 being integrally bonded to the first active material non-formation portion 34. The positive electrode tab 35 forms a second active material non-formation portion where an active material layer is not formed on a surface of the positive electrode metal foil 24.

[0043] As in Fig. 5, at a proximal portion 35a of the positive electrode tab 35, rounded portions 35f are formed at corner portions between edge portions of the positive electrode tab 35 in the longitudinal direction P and an edge portion of the first active material non-formation portion 34 in the transverse direction Q. The rounded portions 35f, 35f are formed at both edge portions of the proximal portion 35a in the longitudinal direction P. With such a configuration, a width of the proximal portion 35a in the longitudinal direction P gradually increases as the proximal portion 35a approaches the first active material. By forming such rounded portions 35f, 35f, the stress concentration exerted on the proximal portion 35a of the positive electrode tab 35, particularly on the corner portions of the proximal portion 35a, can be distributed so that breakage of the positive tab 35 at the proximal portion 35a can be suppressed.That is, the strength of the proximal portion 35a of the positive electrode tab 35 can be increased.

[0044] As in Fig. 3 and Fig. As shown in Fig. 4, a plurality of negative electrode tabs 37 (corresponding to the "second tab" in the claims) are also formed on the negative electrode metal foil 26 in the same manner as the positive electrode tabs 35. The negative electrode tabs 37 are formed on the same side as the positive electrode tabs 35, projecting in the lateral direction Q. Most of the portion of the negative electrode tab 37, except for a proximal end portion, is formed in an active material non-formation portion where an active material layer is not formed on the surface of the negative electrode metal foil 26.

[0045] As in Fig. As shown in Fig. 3, the electrode assembly 20, which is formed by winding the positive electrode sheet 21, the negative electrode sheet 22, and the separators 23, 23 in a state where the positive electrode sheet 21 and the negative electrode sheet 22 are arranged to overlap with the separator 23, 23 therebetween, includes a positive electrode tab bundle 55 (corresponding to the "first tab bundle" in the claims) formed by stacking a plurality of positive electrode tabs 35. The positive electrode tab bundle 55 is formed on a flat portion 20c of the electrode assembly 20.

[0046] The negative electrode tabs 37 are spaced apart from the positive electrode tabs 35 in the longitudinal direction P, so that the positive electrode tabs 35 and the negative electrode tabs 37 cannot overlap. In the electrode assembly 20 in a wound state, the majority of the negative electrode tabs 37 are formed to overlap. With such a configuration, a negative electrode tab bundle 57 is formed, which constitutes the second tab bundle.

[0047] The positive electrode tab bundle 55 and the negative electrode tab bundle 57 each protrude from an end surface portion 20a (the end surface portion on an upper side in Fig. 3) of the electrode assembly 20. Furthermore, the positive electrode tab bundle 55 and the negative electrode tab bundle 57 each protrude from a section (a viewer side in Fig. 3) of the pair of flat portions 20c, 20c with respect to a center line Y extending in the longitudinal direction when the end surface portion 20a of the electrode assembly 20 is viewed in the direction in which the winding axis X extends.

[0048] As in Fig. 2, the positive electrode tab bundle 55 projecting from one flat portion 20c of the electrode assembly 20c is connected to the positive electrode current collector 15 in a state where the positive electrode tab bundle 55 is bent downwardly toward the other flat portion 20c side in the thickness direction Z (the direction orthogonal to the winding axis X and the center line Y) of the electrode assembly 20.

[0049] In such a state, the respective positive electrode tabs 35 constituting the positive electrode tab bundle 55 are curved at the proximal portions 35a thereof (portions ranging from the proximal ends to the intermediate portions), and the distal end side portions 35b (portions ranging from the distal ends 35c to the intermediate portions) of the respective positive electrode tabs 35b face an upper side of the end surface portion 20a of the electrode assembly 20 and, at the same time, are arranged along a lower side of the second flat plate portion 15c of the positive electrode current collector 15.

[0050] The positive electrode tab bundle 55 is connected to the lower side of the second flat plate portion 15c of the positive electrode current collector 15c, for example, by ultrasonic welding.

[0051] In such a configuration, the respective positive electrode tabs 35 are electrically connected to the external terminal 11 of the positive electrode via the positive electrode current collector 15.

[0052] Although not shown in the drawing, the negative electrode tabs 37 are also electrically connected to the external terminal 12 (see Fig. 1) the negative electrode through the negative current collector (not shown in the drawing) in a state where the negative electrode tabs 37 are bent in the same way as the positive electrode tabs 35.

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

[0054] Fig. 5 is an enlarged view showing the positive electrode tab 35 and portions around the positive electrode tab 35 when viewed from a surface side of the positive electrode sheet 21. Fig. 6 is a cross-sectional view of the first active material non-formation portion 34 and portions around the first active material non-formation portion 34 at a portion shifted from the positive electrode tab 35 in the longitudinal direction P, taken along a line BB in Fig. 5, looking in longitudinal direction P. Fig. Fig. 7 is a cross-sectional view of the positive electrode tab 35 and portions around the positive electrode tab 35 taken along a line CC in Fig. 5 looking in the longitudinal direction P. Fig. Fig. 8 is a cross-sectional view of the positive electrode tab 35 and portions around the positive electrode tab 35 taken along a line DD in Fig. 5 looking in a projection direction (transverse direction Q) of the positive electrode tab 35.

[0055] As in Fig. 6 and Fig. 7, the negative active material layer 27 is arranged to protrude more outward in the transverse direction Q than the positive active material layer 25. With such a configuration, when the energy storage device 1 is a lithium-ion battery, lithium ions emitted from the positive active material layer 25 at the time of charging the energy storage device 1 can easily be trapped by the negative active material layer 27.

[0056] As in Fig. 5 to Fig. As shown in Fig. 8, the insulating layer 40 is formed on the surface of the positive electrode metal foil 24 such that the insulating layer 40 is disposed adjacent to the edge portion of the positive active material layer 25 along an edge portion of the positive active material layer 25 in the transverse direction Q. The insulating layer 40 is formed on both surfaces of the positive electrode metal foil 24. The insulating layer 40 includes a first insulating layer portion 41 formed on the first active material non-formation portion 34 of the positive electrode metal foil 24, and a second insulating layer portion 42 formed on the positive electrode tab 35 constituting the second active material non-formation portion.

[0057] As in Fig. 5 and Fig. As shown in Figure 6, the first insulating layer portion 41 is formed on surfaces of the first active material on both sides in the same manner. On each surface of the first active material non-formation portion 34, the first insulating layer portion 41 is formed along an upper edge portion of the positive active material layer 25 in the lateral direction Q and covers an upper edge portion of the positive active material layer 25.

[0058] The first insulating layer portion 41 is formed in a projecting manner from an upper end surface 24a of the positive electrode metal foil 24 in the transverse direction Q, and covers the upper end surface 24a. The first insulating layer portion 41 is formed over the entire length of the first active material non-formation portion 34 in the longitudinal direction P. With such a configuration, surfaces of the first active material non-formation portion 34 on both sides and the upper end surface 24a of the first active material non-formation portion 34 are completely covered by the first insulating layer portion 41.

[0059] As in Fig. As shown in FIG. 5, the second insulating layer portion 42 is formed in a region including the proximal portion 35a of the positive electrode tab 35. More specifically, the second insulating layer portion 42 is formed on a portion of the positive electrode tab 35 ranging from a proximal end to an intermediate portion. A distal end portion 35b of the positive electrode tab 35 is exposed without being covered by the insulating layer 40, so that the distal end portion 35b and the above-mentioned current collector 15 can be connected to each other.

[0060] As in Fig. As shown in Fig. 7, the second insulating layer portion 42 is formed similarly on both surfaces of the positive electrode tab 35. On the respective surfaces of the positive electrode tab 35, the second insulating layer portion 42 is integrally bonded to an outer side of the first insulating layer portion 41 in the transverse direction Q. In the transverse direction Q, an upper edge portion 42a of the second insulating layer portion 42 is positioned outside an upper edge portion 22a of the negative electrode sheet 22a and an upper edge portion 23a of the separator 23.

[0061] As described above, since the proximal portion 35a of the positive electrode tab 35 is covered by the insulating layer 40, the proximal portion 35a can be reinforced by the insulating layer 40, suppressing the occurrence of short circuits. The positive electrode tab 35 is, as described above (see Fig. 2), for connection to the current collector 15, so that stress can be concentrated on the proximal portion 35a, which is curved due to bending. However, the proximal portion 35a is reinforced by the insulation layer 40, so that the rigidity of the positive electrode tab 35 can be increased, thus increasing the durability of the positive electrode tab.

[0062] Furthermore, the rigidity of the proximal portion 35a of the positive electrode tab 35 is increased by the insulation layer 40, and therefore, it is possible to suppress deflection of the positive electrode tab 35, which deforms in a thickness direction R of the positive electrode tab 21 at the time of winding the positive electrode tab 21. Accordingly, when the plurality of positive electrode tabs 35 are overlapped by winding the positive electrode sheet 21, hooking engagement between the positive electrode tabs 35 occurs minimally, so that breakage of each positive electrode tab 35 can be suppressed. Furthermore, as described above, the rounded portions 35f, 35f are formed on the proximal portion 35a, and therefore, even if stress or strain is applied at the time of winding the positive electrode sheet 21, the positive electrode tab 35 can be suppressed.mechanical stress is applied to the positive electrode sheet 21, the stress concentration on the proximal portion 35a is reduced, so that the strength of the proximal portion 35a is further increased.

[0063] As in Fig. 8, the second insulating layer portion 42 of the insulating layer 40 protrudes outward from the positive electrode tab 35 on both sides in the longitudinal direction P and covers side edge surfaces 35d, 35e on both sides of the positive electrode tab 35. In such a configuration, the proximal portion 35a of the positive electrode tab 35 is formed such that surfaces of the positive electrode tab 35 on both sides and side edge surfaces 35d, 35e of the positive electrode tab 35 on both sides are covered by the second insulating layer portion 42.

[0064] An insulating material with high electrical resistance is used as the material for forming the insulating layer 40. A specific material used for forming the insulating layer 40 can be, for example, a mixture of inorganic and / or organic particles and a binder. For example, particles of aluminum oxide (Al2O3), SiO2, ZrO2, TiO2, or MgO are used as inorganic particles, while polyimide powder is used as organic particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide, or polyamide are used as the binder.

[0065] As in Fig. 6 and Fig. As shown in Figure 7, the insulating layer 40 is arranged such that the insulating layer 40 faces the negative active material layer 27 with the separator 23 therebetween. Specifically, the second insulating layer portion 42 of the insulating layer 40 protrudes from the upper edge portion 23a of the separator 23a in the transverse direction Q.Accordingly, even if a portion where the separator 23 is not formed between the first active material non-formation portion 34 and the proximal portion 35a of the positive electrode tab 35 of the positive electrode sheet 21 and the negative active material layer 27 due to various causes including positional displacement, shrinkage, or breakage of the separator 23, so that the positive electrode sheet 21 and the negative electrode sheet 22 are accidentally brought into contact with each other, the insulation layer 40 covering a metal portion of the positive electrode sheet 21 is disposed between the metal foil 24 at the first active material non-formation portion 34 and the positive electrode tab 35 and the negative active material layer 27, therefore, the occurrence of a short circuit can be prevented.

[0066] As in Fig. 6 and Fig. 8, the insulating layer 40 covers not only the surfaces of the first active material non-formation portion 34 and the proximal portion 35a of the positive electrode tab 35 on both sides, but also the upper end surface 24a of the first active material non-formation portion 34 and the side edge surfaces 35d, 35e of the positive electrode tab 35e, therefore further effectively suppressing the occurrence of short circuits.

[0067] Assuming that a metal such as copper, which melts at a positive electrode potential, is mixed into the positive electrode metal foil 24, this metal melts on the positive electrode metal foil 24. When this molten metal precipitates on the negative electrode sheet 22 and the precipitate of the metal grows and is brought into contact with the positive electrode sheet 21, then a short circuit occurs.

[0068] However, according to this embodiment, as shown in Fig. 6 and Fig. 7, the positive electrode metal foil 24 is covered by the insulation layer 40, and thus the melting of metal on the positive electrode metal foil 24 arranged in the vicinity of the negative electrode sheet 22 can be prevented, so that the precipitation of metal on the negative electrode sheet 22 can be suppressed, whereby the occurrence of short circuits due to the metal precipitation can be prevented.

[0069] Furthermore, the upper end surface 24a of the first active material non-formation portion 34 is covered by the insulating layer 40, so that while suppressing a short circuit at the upper end surface 24a, the upper end surface 24a can be easily located near the upper edge portion 23a of the separator 23a located outside the upper end surface 24a in the transverse direction Q. Accordingly, the positive electrode metal foil 24 can be expanded in the transverse direction Q to increase the battery capacity.

[0070] The positive electrode tab 35 is formed by cutting the positive electrode metal foil 24 into a predetermined shape. Specifically, the positive electrode tabs 35 can be formed by cutting portions of the positive electrode metal foil 24, except for portions of the positive electrode metal foil 24 corresponding to the positive electrode tabs 35 at an edge portion of the positive electrode metal foil 24 in the transverse direction Q.

[0071] The above-mentioned upper end surface 24a of the first active material non-formation portion 34 and the side edge surfaces 35d, 35e of the positive electrode tab 35d, 35e are formed by cutting the positive electrode metal foil 24 as described above, after which the insulating layer 40 is formed. In this way, the formation of the insulating layer 40 occurs after cutting the positive electrode metal foil 24, so the end surface 24a of the first active material non-formation portion 34 and the side edge surfaces 35d, 35e of the positive electrode tab 35d, 35e can be covered by the insulating layer 40.

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

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

[0074] For example, in the above-mentioned embodiment, the description is made with respect to the energy storage device 1 comprising a so-called winding-type electrode assembly 20. However, the present invention also applies to an energy storage device comprising a so-called stack-type electrode assembly 120 (corresponding to the “layered product” in the claims), as shown, for example, in Fig. 9 is shown.

[0075] The Fig.The electrode assembly 120 shown in FIG. 9 is a layered product formed of a plurality of positive electrode sheets 121 (corresponding to "first electrode sheet" in the claims) and a plurality of negative electrode sheets 122 (corresponding to "second electrode sheet" in the claims), wherein the positive electrode sheet 121 and the negative electrode sheet 122 are alternately stacked with a separator 123 interposed therebetween. Each positive electrode sheet includes a first active material non-formation portion 34 and a positive electrode tab 35 forming a second active material non-formation portion in the same manner as the above-mentioned embodiment, and each negative electrode sheet 122 includes a negative electrode tab 37 in the same manner as the above-mentioned embodiment.The electrode assembly 120 includes: a positive electrode tab bundle formed by stacking the positive electrode tabs 35 formed on the respective positive electrode sheets 121; and a negative electrode tab bundle formed by stacking the negative electrode tabs 37 formed on the respective negative electrode sheets 122.

[0076] Also in such a stacked-type electrode assembly 120, by forming an insulating layer 40 on the first active material non-formation portion 34 and positive electrode tabs 35 of each positive electrode sheet 121 in the same manner as the aforementioned embodiment, the energy storage device of this embodiment can obtain substantially the same advantageous effects as the aforementioned embodiment, such as an effect that a proximal portion of the tab 35, which is subjected to stress concentration by bending of the positive electrode tab 35, can be reinforced by an insulating layer.

[0077] Furthermore, in the above-mentioned embodiment, the description was made using the example of the case where the "first direction" in which the edge portion of the positive electrode sheet 21 forming the first active material non-formation portion 34 extends and the "second direction" in which the positive electrode tab 35 protrudes from the edge portion are orthogonal to each other. However, in the present invention, the second direction may be inclined with respect to the direction orthogonal to the first direction.

[0078] In the above embodiment, the description was made using the example of the case where the first electrode sheet on which the insulation layer is formed is the positive electrode sheet. However, the present invention also applies to the case where the first electrode sheet is a negative electrode sheet.

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

[0080] In the present invention, the insulating layer formed on the surface of the metal foil of the first electrode sheet may be formed overlappingly on the surface of the edge portion of the active material layer or may be formed on the entire surface of the active material layer by overcoating.

[0081] In the above embodiment, the description was made using the example of a case where the insulating layer is formed not only on the surfaces of the metal foil of the first electrode sheet but also on the end surfaces of the metal foil of the first electrode sheet. However, in the present invention, the insulating layer may not always be formed on the end surfaces of the metal foil. If the insulating layer is not formed on the end surfaces of the metal foil, the cutting of the first electrode sheet to form the first tab may be performed after the insulating layer is formed on the surfaces of the metal foil.

[0082] Furthermore, in the above-mentioned embodiment, the description was made taking as an example the case where the rounded portions are formed on the proximal portion of the first tab. However, in the present invention, the rounded portions do not always need to be formed on the proximal portion of the first tab. List of reference symbols 1 energy storage device 2 external connection positive electrode 15 Current collector with positive electrode 20 Electrode arrangement (winding body) 20c flat section 20d curved section 21 Positive electrode sheet (first electrode sheet) 22 Negative electrode sheet (second electrode sheet) 22a Edge section of the negative electrode sheet 23 Separator 23a Edge section of the separator 24 positive electrode metal foil 24a End face of the positive electrode metal foil 25 Positive active material layer 34 first active material non-training section 35 Positive electrode tab (first tab) (second active material non-training section) 35a proximal section of the positive electrode tab 35c distal end of the positive electrode tab 35d, 35e Side edge surface of the positive electrode tab 37 Negative electrode tab (second tab) 40 insulation layer 41 first insulation layer section 42 second insulation layer section 42a Edge section of the second insulation layer section 55 positive electrode tab bundles (first tab bundle) 57 Negative electrode tab bundle (second tab bundle) 120 electrode arrangement (layered product) 121 Positive electrode sheet (first electrode sheet) 122 Negative electrode sheet (second electrode sheet) 123 Separator P Longitudinal direction of the blade (first direction) Q Transverse direction of the sheet (second direction) X winding axis QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 5354042

[0005]

Claims

[1] Energy storage device comprising: a first electrode sheet; and a second electrode sheet stacked on the first electrode sheet, wherein a separator is disposed between the first electrode sheet and the second electrode sheet, and having a polarity different from a polarity of the first electrode sheet, wherein the first electrode sheet comprises: a metal foil having an edge portion extending linearly in a first direction and a first tab extending 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 insulation layer formed on the surface of the metal foil, wherein a portion extending along the edge portion and the first tab of the metal foil are formed into an active material non-formation portion in which the active material layer is not formed, and wherein the insulating layer is formed on the active material non-formation portion. [2] The energy storage device according to claim 1, wherein the insulation layer is formed in a region of the active material non-formation portion including a proximal portion of the first tab. [3] The energy storage device according to claim 1, wherein the insulation layer is formed in a portion where the active material layer is not formed, which includes at least a proximal end of the first tab. [4] The energy storage device of claim 2, wherein the first tab is rounded at its proximal portion. [5] The energy storage device according to claim 2 or 3, wherein the first tab is rounded at a corner portion of the first tab. [6] The energy storage device according to claim 4 or 5, wherein the insulation layer is formed in a portion including the rounded portions. [7] The energy storage device according to any one of claims 2 to 6, further comprising a current collector electrically connecting the first electrode sheet to an external terminal, wherein the first tab is connected to the current collector in a bent state. [8] The energy storage device according to any one of claims 2 to 6, further comprising a current collector electrically connecting the first electrode sheet to an external terminal, wherein the first tab is curved and connected to the current collector. [9] The energy storage device according to claim 7 or 8, wherein a distal end side portion of the first tab extends along a third direction which is perpendicular to the first direction and the second direction. [10] The energy storage device according to any one of claims 1 to 9, wherein the insulation layer is arranged with the active material layer in the second direction and is integrally connected with the active material layer. [11] The energy storage device according to any one of claims 1 to 10, wherein the insulation layer is in contact with the active material layer in a thickness direction of the first electrode sheet. [12] The energy storage device according to any one of claims 1 to 10, wherein the insulation layer is further formed on the active material layer [13] The energy storage device according to any one of claims 2 to 12, wherein a portion of the insulating layer formed on a surface of the first tab extends from an edge portion of the separator in the second direction. [14] The energy storage device according to any one of claims 2 to 12, wherein an upper edge portion of the insulation layer is formed outside an upper edge portion of the separator. [15] The energy storage device according to any one of claims 1 to 14, wherein the insulation layer is also formed on an end surface of the metal foil in the active material non-formation portion. [16] The energy storage device according to any one of claims 1 to 15, wherein the second electrode sheet has an edge portion extending linearly in the first direction and a second tab extending in the second direction from the edge portion, and wherein the first tab and the second tab protrude to the same side in the second direction and are arranged in a spaced-apart manner in the first direction. [17] The energy storage device according to any one of claims 1 to 16, wherein the first electrode sheet has a plurality of the first tabs arranged in a spaced manner in the first direction, wherein a winding body is formed by winding the first electrode sheet and the second electrode sheet around an axis parallel to the second direction, while the first electrode sheet and the second electrode sheet are formed so as to overlap with the separator arranged therebetween, and wherein the winding body has a first tab bundle formed by stacking the plurality of first tabs. [18] The energy storage device according to claim 17, wherein the winding body comprises a pair of flat portions extending in a straight manner parallel to each other when viewed in a direction in which the axis extends, and a pair of bent portions connecting the pair of flat portions to each other, and wherein the first tab bundle is supplied to the flat portion. [19] The energy storage device according to any one of claims 1 to 16, wherein the energy storage device comprises a layered product formed of a plurality of the first electrode sheets and a plurality of the second electrode sheets, the first electrode sheet and the second electrode sheet being alternately stacked with the separator disposed between the first electrode sheet and the second electrode sheet, and the layered product comprises the first tab bundle formed by stacking the first tabs each formed on the plurality of the first electrode sheets.

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