Electricity storage device and manufacturing method thereof

Abstract

This electricity storage device is provided with a first electrode including a first current collector in the shape of an elongate sheet and a first active material layer supported on the first current collector, a second electrode in the shape of an elongate sheet, a separator interposed between the first electrode and the second electrode, a non-aqueous electrolyte, and a first current collecting portion which is electrically connected to the first current collector, wherein: the first electrode, the second electrode, and the separator constitute a columnar wound body; one end portion in the longitudinal direction of the first current collector is a first exposed portion which does not include the first active material layer and which protrudes from one end surface of the wound body; the first current collecting portion includes a porous metal portion, and one or more projecting portions which are press fitted into the porous metal portion; and the porous metal portion fills gaps in the first exposed portion.

Description

[Technical Field]

[0001] The present disclosure relates to an electricity storage device and a manufacturing method thereof. [Background technology]

[0002] Patent Document 1 discloses, as an example of an electricity storage device, an electrode group in which a positive electrode and a negative electrode are wound around a cylindrical core with a separator interposed therebetween; a battery can having an opening on the upper side and containing the electrode group and filled with an electrolyte; a battery lid disposed on the upper side of the battery can; and a negative electrode current collecting member disposed between the can bottom of the battery can and the lower end of the core, to which a negative electrode tab of the negative electrode is connected and which is joined to the battery can, the negative electrode current collecting member being made of a first metal to which the negative electrode is connected, and which is diffusion-fused to the first metal and which is a conductor of the battery can. The present invention proposes a cylindrical secondary battery in which the negative electrode current collecting member is formed of a clad material integrated with a second metal bonded to the bottom, the first metal being formed of copper or a copper alloy, the second metal being formed of nickel, the negative electrode current collecting member being ring-shaped with an outer peripheral sidewall on the outer periphery, the negative electrode current collecting member having a cylindrical recess formed in the center into which the tip end of the shaft core is inserted, the second metal being bonded to the bottom of the battery can in the cylindrical recess, and the negative electrode tab being bonded to the first metal on the outer peripheral sidewall of the negative electrode current collecting member by ultrasonic welding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2013 / 024774 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of Patent Document 1, current can only be extracted from the portion of the negative electrode where the negative electrode tab is connected, resulting in low current collection efficiency and high connection resistance in the battery.

[0005] On the other hand, a so-called end-face current collection structure has been investigated as a current collection structure for obtaining high output. The end-face current collection structure generally refers to a structure in which the exposed part of the electrode current collector protrudes from the end face of the wound body and is welded to the current collecting plate.

[0006] However, because the current collector is thin, it is necessary to deform the wound current collector, gather it, and weld it to the current collecting plate. Deforming a thin current collector places a large load on the current collector, which can cause it to break. In addition, deforming a wound current collector requires processing such as partially cutting away the exposed part of the current collector or creating slits. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to an energy storage device comprising: a first electrode including a long sheet-like first current collector and a first active material layer supported on the first current collector; a long sheet-like second electrode; a separator interposed between the first electrode and the second electrode; a non-aqueous electrolyte; and a first current collector electrically connected to the first current collector, wherein the first electrode, the second electrode, and the separator form a cylindrical wound body, and one end of the first current collector along the longitudinal direction does not have the first active material layer and is a first exposed portion protruding from one end face of the wound body, and the first current collector has a porous metal portion and one or more protrusions press-fitted into the porous metal portion, and the porous metal portion abuts the first exposed portion.

[0008] Another aspect of the present disclosure relates to a method for manufacturing an electricity storage device, the method including the steps of: preparing a first electrode comprising a long sheet-like first current collector and a first active material layer supported on the first current collector, wherein one end along the longitudinal direction of the first current collector is a first exposed portion that does not have the first active material layer; preparing a long sheet-like second electrode; preparing a separator to be interposed between the first electrode and the second electrode; forming a cylindrical wound body from the first electrode, the second electrode, and the separator, and causing the first exposed portion to protrude from one end surface of the wound body; applying a conductive paste containing metal particles to the first exposed portion and solidifying or curing the conductive paste to form a porous metal portion that fills gaps in the first exposed portion; and press-fitting one or more protrusions into the porous metal portion to form a first current collecting portion. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to obtain a highly reliable electricity storage device with low connection resistance and small load on the current collector. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a vertical cross-sectional view illustrating an example of a configuration of an electric storage device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a plan view showing the configuration of a first electrode. [Figure 3] 10A and 10B are a plan view and a longitudinal cross-sectional view showing another configuration of the first electrode. [Figure 4] FIG. 4 is a plan view showing the configuration of a second electrode. [Figure 5] FIG. 2 is a perspective view showing the appearance of a wound body included in an electricity storage device according to an embodiment of the present disclosure. [Figure 6]FIG. 10 is a process diagram showing a process for winding the first electrode and the second electrode with a separator interposed therebetween while applying a conductive paste to the first exposed portion of the first electrode. [Figure 7] 10A to 10C are diagrams showing variations in the application pattern of the conductive paste applied to the first exposed portion of the first electrode. [Figure 8] FIG. 10 is a process diagram showing how the protrusions of the first current collector plate are press-fitted into the porous metal portion filling the gaps in the first exposed portion, and then how the first current collector plate is welded to the bottom of the bottomed case. [Figure 9] FIG. 3 is a cross-sectional view showing an example of a first current collector plate having a through hole. [Figure 10] FIG. 4 is a cross-sectional view showing an example of a protrusion. [Figure 11] 10A and 10B are diagrams showing protrusions protruding from the bottom of the bottomed case. [Figure 12] FIG. 10 is a process diagram showing the process of placing the first current collector plate on the first end face of the wound body after applying conductive paste to the first current collector plate from which the protruding projections protrude. [Figure 13] FIG. 10 is a perspective view showing a wound body having first exposed portions subdivided by slits. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described. Note that in the following description, examples of embodiments of the present disclosure will be described, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values, materials, etc. may be exemplified, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure can be obtained.

[0012] <Electricity storage device> The power storage device according to the present disclosure includes a first electrode in the form of a long sheet, a second electrode in the form of a long sheet, a separator interposed between the first electrode and the second electrode, and a non-aqueous electrolyte or electrolytic solution. The first electrode and the second electrode are wound with the separator interposed therebetween to form a columnar wound body.

[0013] The first electrode includes a long sheet-like first current collector and a first active material layer supported on the first current collector. One longitudinal end (one widthwise end) of the first current collector is a first exposed portion that does not have the first active material layer. The first exposed portion protrudes from one end face (hereinafter also referred to as the "first end face") of the wound body.

[0014] The power storage device according to the present disclosure includes a first current collector electrically connected to a first current collector. The first current collector has a porous metal portion and one or more protrusions press-fit into the porous metal portion. The first current collector forms a path for current drawn from the first current collector to an external terminal. The larger the area of ​​the first exposed portion electrically connected to the first current collector, the smaller the connection resistance.

[0015] The porous metal portion abuts against the first exposed portion. It can also be said that the porous metal portion is disposed in the gaps of the first exposed portion. The gaps of the first exposed portion refer to the multiple annular gaps formed between the first exposed portions when the first electrode is spirally wound. The porous metal portion is disposed, for example, so as to fill the gaps of the first exposed portion that were originally present, so that the first exposed portion itself is not subjected to excessive load from the porous metal portion. Furthermore, the contact area between the porous metal portion that fills the gap and the first exposed portion is sufficiently large. Therefore, the connection resistance at the interface between the porous metal portion and the first exposed portion is small.

[0016] The one or more protrusions press-fitted into the porous metal portion bite into the porous metal portion, and can be firmly bonded to the porous metal portion. Such a strong bond ensures the reliability of current collection. Meanwhile, only the portion of the porous metal portion into which the protrusions are press-fitted undergoes selective plastic deformation. Therefore, compared to a configuration in which the current collector plate is pressed against the first exposed portion and the current collector plate and the first exposed portion are welded, the load on the first exposed portion (i.e., the first current collector) can be reduced. Therefore, high reliability is maintained over a long period of time. Note that the first exposed portion that the porous metal portion abuts may be welded to a current collector plate that does not have any protrusions. This configuration can also improve rigidity compared to conventional first exposed portions.

[0017] The porous metal portion may be formed, for example, from a conductive paste containing metal particles. The conductive paste is applied so as to cover at least a portion of the first end surface of the wound body. Because the conductive paste has fluidity, it can be applied without placing a large load on the first exposed portion. In this case, the porous metal portion is composed of an aggregate of multiple metal particles, i.e., a solidified or hardened conductive paste.

[0018] The porous metal portion (solidified or hardened conductive paste) formed from the conductive paste is composed of multiple metal particles and has many voids inside, making it susceptible to plastic deformation. This further reduces the load on the first exposed portion (i.e., the first current collector) when the protrusion is pressed into place.

[0019] In addition to metal particles, the conductive paste may contain organic components such as a solvent, a resin, etc. When the conductive paste contains a non-volatile organic component, the porous metal portion may also contain an organic component.

[0020] The conductive paste containing a volatile solvent is preferably a conductive paste that solidifies by volatilizing the solvent. In this case, most of the porous metal portion (e.g., 80 mass % or more) is composed of metal particles. The conductive paste containing a resin is preferably a conductive paste containing a curable resin. In this case, a strong porous metal portion can be formed by curing the curable resin. The curable resin may be a thermosetting resin.

[0021] The metal particles may have an average particle size (median diameter) of 0.1 μm or more and 10 μm or less in the particle size distribution based on volume. Multiple types of metal particles with different average particle sizes may be mixed. The metal species constituting the metal particles are appropriately selected depending on the type of electricity storage device, the polarity of the first electrode, the material of the first current collector, etc.

[0022] The thermosetting resin is preferably a resin composition containing an epoxy resin as a main component, but is not particularly limited thereto.

[0023] The thickness of the porous metal portion is desirably smaller than the width of the first exposed portion in the short-side direction (width direction) of the first current collector, and may be 10% or more and less than 100% of the width of the first exposed portion. Here, the thickness of the porous metal portion is the average value of measurements taken at 10 arbitrary locations.

[0024] The protrusions may be electrically connected to the external terminal of the first electrode (hereinafter referred to as the first terminal). For example, the protrusions may protrude from a first current collector plate that is electrically connected to the first terminal. The first current collector plate is typically plate-shaped.

[0025] When the protrusions protrude from the first current collector plate, the protrusions may have through-holes that penetrate the first current collector plate. In this case, the nonaqueous electrolyte or electrolytic solution can flow through the through-holes. For example, the through-holes and the protrusions standing on the edges of the through-holes may be formed simultaneously by drilling a plurality of holes in the plate-shaped metal member.

[0026] The protrusion may protrude from the bottom of the bottomed case. The bottomed case is a case that houses at least the wound body (i.e., the first electrode, the second electrode, and the separator) and the nonaqueous electrolyte or the electrolytic solution. In this case, the bottom of the bottomed case also serves as the first current collector, and a separate first current collector is not required. This is advantageous for reducing manufacturing costs and improving battery capacity.

[0027] The shape of the protrusion is not particularly limited, but it is desirable that the tip is sharply pointed. The tip of the protrusion may be hook-shaped. Hook-shaped broadly includes shapes with an engaging portion at the tip, shapes with a bent portion at the tip, and the like. The engaging portion is a portion that engages with the porous metal portion when the protrusion pressed into the porous metal portion is pulled out. The engaging portion protrudes in a direction different from the direction in which the protrusion protrudes.

[0028] Although one protrusion may be used, it is preferable to have a plurality of protrusions (for example, three or more). It is preferable to dispose the plurality of protrusions as dispersedly as possible.

[0029] The height of the protrusions may be equal to or less than the thickness of the porous metal portion, or may be equal to or less than 20% of the thickness of the porous metal portion. The height of the protrusions may be, for example, 50 μm to 500 μm. Here, the height of the protrusions is the average value of the measured maximum heights of all the protrusions.

[0030] The first exposed portion may be folded back at least once. The thickness of the folded portion formed by folding back is about twice the thickness before folding, and the contact area of ​​the folded portion with the conductive paste is also about twice as large, including the inner surface of the folded portion. This makes it easier for more conductive paste to adhere to the first exposed portion, thereby strengthening the connection between the porous metal portion and the first exposed portion.

[0031] At least a portion of the first exposed portion may be subdivided by a plurality of slits extending in the short-side direction (width direction) of the first current collector. In this case, the first exposed portion is subdivided into a plurality of strips and has a brush-like shape protruding from the first end face. As a result, the contact area between the conductive paste and the first exposed portion can be significantly increased.

[0032] Furthermore, the porous metal portions formed in the first exposed portion may be formed intermittently in the winding direction of the first exposed portion. With this configuration, among the multiple porous metal portions aligned in the winding direction, the electrolyte (non-aqueous electrolyte) can easily penetrate through the gaps between adjacent porous metal portions. This makes it easier for the electrolyte to be impregnated into the wound body. Furthermore, compared to porous metal portions that extend continuously in the winding direction, stress caused by bending the porous metal portions during winding can be reduced.

[0033] The porous metal portions formed at predetermined intervals may be aligned so as to overlap one another in the radial direction of the winding when the end face of the winding is viewed from the winding axis direction. This configuration makes it possible to increase the bonding area between the end face of the winding and the current collector plate when extending the welding mark in the radial direction when joining the end face and the current collector plate. Furthermore, the porous metal portions increase the heat capacity of the end face, making it possible to reduce damage caused by heat generated from the end face to the inside of the winding during welding.

[0034] <Method of manufacturing an electricity storage device> The manufacturing method of the energy storage device according to the present disclosure includes the steps of (i) preparing a first electrode, (ii) preparing a second electrode, (iii) preparing a separator to be interposed between the first electrode and the second electrode, (iv) forming a cylindrical wound body from the first electrode, the second electrode, and the separator, and causing a first exposed portion to protrude from one end face (first end face) of the wound body, (v) applying a conductive paste containing metal particles to the first exposed portion and solidifying or curing the conductive paste to form a porous metal portion that fills the gaps in the first exposed portion, and (vi) pressing one or more protrusions into the porous metal portion to form a first current collecting portion.

[0035] The first electrode includes a first current collector in the form of a long sheet and a first active material layer supported on the first current collector. One longitudinal end of the first current collector is a first exposed portion that does not have the first active material layer.

[0036] The step of applying the conductive paste to the first exposed portion may be performed when forming the wound body. For example, the first electrode and the second electrode may be wound with a separator interposed therebetween while the conductive paste is applied to the first exposed portion of the first electrode before being wound. This allows the first electrode and the second electrode to be wound with the separator interposed therebetween in parallel with the application of the conductive paste to the first exposed portion. In this case, a conductive paste application device such as a dispenser may be additionally installed in a conventional device for forming the wound body. This does not result in a major change to the manufacturing process or a significant increase in the required time. Alternatively, the conductive paste may be applied to the first exposed portion before winding.

[0037] Before applying the conductive paste to the first exposed portion of the first electrode, the first exposed portion may be folded at least once. In this way, by incorporating the folding of the first exposed portion and the application of the conductive paste to the first exposed portion into the winding process, a wound body can be efficiently formed. The device for folding the first exposed portion may be additionally installed before the device for applying the conductive paste. The solidification or curing of the conductive paste may be performed before or after the first exposed portion to which the conductive paste has been applied is wound.

[0038] Alternatively, after the winding body is constructed, a step of applying a conductive paste to the first exposed portion may be performed. Specifically, a first current collector plate having protrusions is prepared, and the conductive paste is applied to the surface of the first current collector plate from which the protrusions protrude to form a coating film. Next, the first current collector plate is placed on the first end surface of the winding body with the coating film interposed between them. At this time, the conductive paste penetrates into the gaps in the first exposed portion, and the protrusions are pressed into (or embedded in) the conductive paste. Thereafter, the conductive paste is solidified or hardened to form a porous metal portion and a protrusion pressed into the porous metal portion.

[0039] As described above, the step of press-fitting one or more protrusions into the porous metal portion to form the first current collecting portion may be performed before or after the conductive paste is solidified or hardened. The formed porous metal portion does not have fluidity but has flexibility that allows it to be plastically deformed. Therefore, the protrusions can be press-fitted without applying excessive load to the first exposed portion.

[0040] Although the above-described methods are merely examples, at least according to the above methods, there is no particular need for complex processing such as deforming the first exposed portion, so the first current collector is less likely to break, and it is easy to obtain a highly reliable battery.

[0041] The second electrode may include a second current collector in the form of a long sheet and a second active material layer supported on the second current collector. One longitudinal end (one widthwise end) of the second current collector may be a second exposed portion that does not have the second active material layer, and the second exposed portion may protrude from the other end face of the wound body. A second current collector having a configuration similar to that of the first current collector may also be formed on the other end face of the wound body (the end face opposite the first end face, hereinafter also referred to as the "second end face").

[0042] However, the second current collecting portion may have a configuration other than the above configuration having a porous metal portion and a protrusion portion. The second current collecting portion may have a lead tab extending from the second exposed portion. The lead tab may be cut out from a metal sheet integrally with the second exposed portion and the second current collector, or a separately prepared lead tab may be connected to the second exposed portion. The second current collecting portion only needs to be electrically connected to an external terminal (hereinafter referred to as the second terminal) of the second electrode. The second current collecting portion may have a plate-shaped second current collecting plate electrically connected to the second exposed portion.

[0043] The other longitudinal end of the first current collector may be a third exposed portion that does not have the first active material layer, and the other longitudinal end of the second current collector may be a fourth exposed portion that does not have the second active material layer. In this case, the third exposed portion and the fourth exposed portion do not typically protrude from the end face of the wound body and are typically covered and protected by an insulating member.

[0044] The power storage device according to the present disclosure is suitable for use as, for example, a nonaqueous electrolyte secondary battery, an alkaline storage battery, a capacitor, etc., and particularly contributes to increasing the output of nonaqueous electrolyte batteries. Examples of nonaqueous electrolyte batteries include lithium-ion secondary batteries and all-solid-state batteries. In this case, one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode. Furthermore, one of the first current collector and the second current collector is a positive electrode current collector made of, for example, aluminum or an aluminum alloy, and the other is a negative electrode current collector made of, for example, copper or a copper alloy.

[0045] Hereinafter, a lithium ion secondary battery, which is an example of the power storage device according to this embodiment, will be described in more detail with reference to the drawings.

[0046] Fig. 1 is a longitudinal cross-sectional view showing the configuration of a battery (lithium ion secondary battery) that is an example of an electricity storage device according to an embodiment of the present disclosure. Fig. 2 is a plan view showing the configuration of a first electrode 10, which is one of a positive electrode and a negative electrode. Fig. 3 is a plan view showing the configuration of another first electrode 10A. Fig. 4 is a plan view showing the configuration of a negative electrode 20, which is the other of a positive electrode and a negative electrode. Fig. 5 is a perspective view showing the appearance of a wound body 100 according to this embodiment.

[0047] Battery 200 includes a columnar wound body 100, a non-aqueous electrolyte (not shown), a metal case 210 with a bottom that accommodates wound body 100 and the non-aqueous electrolyte, and a sealing plate 220 that seals the opening of case 210. A gasket 221 is disposed on the periphery of sealing plate 220, and the inside of case 210 is sealed by crimping the open end of case 210 to gasket 221. Wound body 100 is formed by winding long sheet-like first electrode 10 and long sheet-like second electrode 20 with long sheet-like separator 30 interposed therebetween.

[0048] As shown in FIG. 2, the first electrode 10 includes a first current collector 11 and a first active material layer 12 supported thereon. The first active material layer 12 is formed on both sides of the first current collector 11. However, a first exposed portion 11x that does not have the first active material layer 12 is formed at one end along the longitudinal direction of the first current collector 11. The first exposed portion 11x protrudes from one end face (first end face) of the wound body 100. Note that an exposed portion other than the first exposed portion 11x may also be formed on the first current collector 11.

[0049] A first current collecting portion 13 electrically connected to the first current collecting body 11 is formed on the first end face side of the wound body 100. The first current collecting portion 13 includes a porous metal portion PM and a first current collecting plate 132. The porous metal portion PM fills the gaps in the first exposed portion 11x. The contact area between the porous metal portion PM filling the gaps and the first exposed portion 11x is necessarily sufficiently large.

[0050] 3A is a plan view showing the configuration of another first electrode 10A, and FIG. 3B is a longitudinal cross-sectional view taken along line bb of the first electrode 10A. In the first electrode 10A, the first exposed portion 11x of the first current collector 11 is folded back once to form a folded portion 11y. In the case of the first electrode 10A having the folded portion 11y, the contact area between the first exposed portion 11x and the porous metal portion PM is further increased.

[0051] A plurality of protrusions PR protrude from the first current collector plate 132. The protrusions PR are press-fit into the porous metal part PM. The first current collector plate 132 is connected to the inner surface of the bottom of the case 210 via a connection terminal 133. Therefore, the case 210 functions as a first terminal.

[0052] As shown in FIG. 4, the second electrode 20 includes a second current collector 21 and a second active material layer 22 supported thereon. The second active material layer 22 is formed on both sides of the second current collector 21. However, a second exposed portion 21x that does not have the second active material layer 22 is formed at one end along the longitudinal direction of the second current collector 21. The second exposed portion 21x protrudes from the other end face (second end face) of the wound body 100. Note that an exposed portion other than the second exposed portion 21x may also be formed on the second current collector 21.

[0053] A second current collecting part 23 electrically connected to the second current collecting body 21 is formed on the second end face side of the wound body 100. The second current collecting part 23 includes a porous metal part PM and a second current collecting plate 232. Hereinafter, the porous metal part of the first current collecting part may be designated as PM1, and the porous metal part of the second current collecting part may be designated as PM2 to distinguish them from each other.

[0054] The porous metal part PM2 fills the gaps in the second exposed part 21x. The contact area between the porous metal part PM2 filling the gaps and the second exposed part 21x is necessarily sufficiently large. If a folded part is formed in the second exposed part 21x, the contact area between the second exposed part 21x and the porous metal part PM2 will be even larger.

[0055] A plurality of second protrusions PR protrude from the second current collector plate 232. The second protrusions PR are press-fit into the second porous metal portion PM2. The second current collector plate 232 is connected to the inner surface of the sealing plate 220 via a current collecting lead 25. Therefore, the sealing plate 220 functions as a second terminal.

[0056] The first and second exposed portions 11x and 21x are hardly deformed because they are not subjected to an excessive load from the porous metal portion PM.

[0057] A sheet-like metal material is used for the positive electrode current collector, which is one of the first current collector 11 and the second current collector 21. The sheet-like metal material may be a metal foil, a porous metal, an etched metal, or the like. Examples of the metal material that can be used include aluminum, an aluminum alloy, nickel, and titanium. The thickness of the positive electrode current collector is, for example, 10 μm to 100 μm.

[0058] A sheet-like metal material is used for the negative electrode current collector, which is the other of the first current collector 11 and the second current collector 21. The sheet-like metal material may be a metal foil, a porous metal, an etched metal, or the like. The metal material may be copper, a copper alloy, nickel, stainless steel, or the like. The thickness of the negative electrode current collector is, for example, 10 μm to 100 μm.

[0059] The positive electrode active material layer, which is one of the first active material layer 12 and the second active material layer 22, contains, for example, a positive electrode active material, a conductive material, and a binder. The positive electrode active material layer is obtained, for example, by applying a positive electrode mixture slurry containing the positive electrode active material, a conductive material, and a binder to both sides of a positive electrode current collector, drying the coating, and then rolling it. The positive electrode active material is a material that absorbs and releases lithium ions. Examples of positive electrode active materials include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides.

[0060] The negative electrode active material layer, which is the other of the first active material layer 12 and the second active material layer 22, contains, for example, a negative electrode active material, a conductive agent, and a binder. The negative electrode active material layer is obtained, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a conductive agent, and a binder to both sides of the negative electrode current collector 21, drying the coating, and then rolling it. The negative electrode active material is a material that absorbs and releases lithium ions. Examples of negative electrode active materials include carbon materials, metal compounds, alloys, and ceramic materials.

[0061] The material of the positive current collector, which is one of the first current collector 132 and the second current collector 232, is, for example, aluminum, aluminum alloy, titanium, stainless steel, etc. The material of the positive current collector may be the same as the material of the positive current collector 11.

[0062] The material of the negative electrode current collector, which is the other of the first current collector 132 and the second current collector 232, is, for example, copper, copper alloy, nickel, stainless steel, etc. The material of the negative electrode current collector may be the same as the material of the negative electrode current collector.

[0063] For example, a microporous film made of a resin such as polyolefin, a woven fabric, or a nonwoven fabric can be used as the separator 30. The thickness of the separator is, for example, 10 to 300 μm, and preferably 10 to 40 μm.

[0064] The non-aqueous electrolyte has lithium ion conductivity and contains, for example, a lithium salt and a non-aqueous solvent that dissolves the lithium salt.

[0065] 5, the wound body 100 is positioned during winding so that the first exposed portion 11x protrudes from one end face (first end face) of the wound body 100 and the second exposed portion 21x protrudes from the other end face (second end face) of the wound body 100. A separator 30 is wound around the outermost periphery of the wound body 100. The outermost periphery of the wound body 100 may be a positive electrode current collector or a negative electrode current collector.

[0066] A conductive paste P1 is applied to the first exposed portion 11x protruding from the first end surface. The conductive paste P1 is solidified or hardened to form a porous metal portion PM1 composed of an aggregate of multiple metal particles. Because the conductive paste P1 has fluidity before solidification or hardening, it spreads over the first exposed portion 11x due to, for example, the action of surface tension, so as to cover at least a portion of the first end surface of the wound body 100.

[0067] A conductive paste P2 is applied to the second exposed portion 21x protruding from the second end face. The conductive paste P2 is solidified or hardened to form a porous metal portion PM2 composed of an aggregate of multiple metal particles. Because the conductive paste P2 before solidifying or hardening has fluidity, it spreads over the second exposed portion 21x, wetting it with the action of surface tension, for example, so as to cover at least a portion of the second end face of the wound body 100.

[0068] One of the conductive pastes P1 and P2, which is applied to the exposed portion of the positive electrode current collector, contains powder of aluminum, aluminum alloy, or the like as metal particles. The other of the conductive pastes P1 and P2, which is applied to the exposed portion of the negative electrode current collector, contains powder of copper, copper alloy, nickel, nickel alloy, or the like as metal particles. The metal particles of the conductive pastes P1 and P2 may have their surfaces coated with another metal.

[0069] 6 conceptually illustrates an example of a process for forming the wound body 100. Here, a case is shown in which the first electrode 10 and the second electrode 20 are wound with the separator 30 interposed therebetween while a conductive paste P1 is applied to the first exposed portion 11x of the first electrode 10 before winding. The second electrode 20 and the separator 30 are shown simply by dashed lines, but a conductive paste P2 may also be applied to the second exposed portion 21x of the second electrode 20 before winding.

[0070] 7 illustrates variations in the application pattern of the conductive paste P1 applied to the first exposed portion 11x of the first electrode 10. The following variations can also be applied to the conductive paste P2 applied to the second exposed portion 11x of the second electrode 20.

[0071] 7A conceptually illustrates (a) the process of forming wound body 100 by continuously applying conductive paste P1 to first exposed portion 11x, and (b) the state of the first end face of the resulting wound body 100. In the embodiment of FIG. 7A, conductive paste P1 is applied to the gaps in first exposed portion 11x so as to cover most (e.g., 90% or more) of the first end face. This makes it difficult for spatter or foreign metal matter to penetrate into the interior of wound body 100 during a subsequent welding process, and forms first current collecting portion 13 with lower resistance.

[0072] 7B conceptually illustrates (a) the process of forming the wound body 100 by intermittently applying the conductive paste P1 to the first exposed portions 11x, and (b) the state of the first end face of the resulting wound body 100. In the embodiment of FIG. 7B, the conductive paste P1 is applied to the gaps in the first exposed portions 11x so as to cover, for example, 50% or more (e.g., 50% or more but less than 90%) of the first end face. This makes it difficult for metal foreign matter to penetrate into the inside of the wound body 100, and also ensures sufficient injectability of the nonaqueous electrolyte.

[0073] FIG. 7C conceptually illustrates (a) a process for forming the wound body 100 by applying the conductive paste P1 to the first exposed portions 11x in spots at predetermined intervals, and (b) a state of the first end face of the resulting wound body 100. In the embodiment of FIG. 7C, the conductive paste P1 is applied to the gaps in the first exposed portions 11x so as to cover less than 50% (e.g., 10% to 50%) of the first end face. This ensures better injectability of the nonaqueous electrolyte. Note that when the conductive paste P1 is distributed radially (in a radial pattern) around the wound body 100, as in the region surrounded by the dashed line X, a thicker conductive path with lower resistance is formed.

[0074] FIG. 8 is a conceptual diagram showing steps ((a) and (b)) of press-fitting the protrusions PR of the first current collector 132 into the porous metal part PM1 filling the gaps in the first exposed part 11x, and then (c) and (d) of welding the first current collector 132 to the bottom of the bottomed case 210. By press-fitting the protrusions PR, the first current collector 132 is firmly connected to the porous metal part PM1, achieving a highly reliable electrical connection. The welding step (d) can be performed by a technique such as laser welding in which a laser LA is irradiated from the outer surface side of the bottom of the case 210.

[0075] 8 illustrates a case in which first current collecting part 13 is connected to the bottom of case 210 and case 210 also serves as the first terminal, but the present invention is not limited to this. First current collecting part 13 may be disposed on the opening side of case 210 and connected to the inner surface of sealing plate 220 via a predetermined current collecting lead. In this case, second current collecting part 23 is connected to the bottom of case 210.

[0076] 9 conceptually illustrates a cross section of one example of the first or second current collector plate 132, 232. A through-hole 132h (232h) penetrating the first or second current collector plate 132, 232 is provided in the portion of the first or second current collector plate 132, 232 that constitutes the protruding portion PR. The through-hole 132h (232h) serves to promote the flow of non-aqueous electrolyte. Providing a through-hole in the protruding portion PR facilitates the flow of non-aqueous electrolyte into the porous metal portion PM or toward the wound body 100 from the porous metal portion PM.

[0077] In the drawings described above, the protrusions are conceptually shown as conical, but there are many variations in the shape of the protrusions. Figure 10 shows another example of a protrusion PR. The protrusion PR has a hook-shaped engagement portion PRC at its tip. The engagement portion PRC serves to prevent the protrusion PR from being pulled out of the porous metal portion PM.

[0078] The first or second current collecting plate 132, 232 is not necessarily required. Fig. 11 conceptually shows a case where a protrusion PR protrudes from the bottom of the bottomed case 210. By forming the protrusion PR on the bottom of the case 210 in this way, the porous metal part PM can be directly connected to the bottom of the case 210. This allows for more effective use of the space inside the case.

[0079] The process of applying the conductive paste P1 or P2 to the first or second exposed portion 11x, 21x may be performed after the winding is completed. FIG. 12 illustrates the process of preparing a first current collector 132 having a protrusion PM (omitted in FIG. 12), applying the conductive paste P1 to the surface of the first current collector 132 from which the protrusion PR protrudes to form a coating, and then placing the first current collector 132 on the first end surface of the already constructed winding 100. When the end surface of the winding 100 is placed on the coating of the conductive paste P1, the fluid conductive paste P1 penetrates into the gaps in the first exposed portion 11x due to the action of surface tension. This facilitates the formation of the first current collector 13. In this process, as shown in FIG. 13, multiple slits may be formed in at least a portion of the first exposed portion 11x in the width direction of the first current collector 11 to subdivide the first exposed portion 11x and form brush-like exposed portions 111x. This significantly increases the contact area between the conductive paste P1 and the first exposed portion 11x, and therefore a more significant reduction in contact resistance can be expected. [Industrial Applicability]

[0080] The power storage device according to the present disclosure has low contact resistance, high output, and high reliability, and is therefore suitable for use in vehicles, for example. While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention. [Explanation of symbols]

[0081] 100: Rolled body 10, 10A: 1st electrode 11: First current collector 11x: 1st exposed part 111x: Brush-like exposed part 11y: Folded part 12: First active material layer 13: First current collecting section 132: First current collecting plate 133: Connection terminal 20:Second electrode 21: Second current collector 21x: 2nd exposed part 22: Second active material layer 23: Second current collecting section 232: Second current collecting plate 25: Current collecting lead 30: Separator 200: Battery (electricity storage device) 210: Case 220: Sealing board 221: Gasket PM: Porous metal part PR:Protrusion

Claims

1. a first electrode including a first current collector in the form of a long sheet and a first active material layer carried on the first current collector; a second electrode in the form of a long sheet; a separator interposed between the first electrode and the second electrode; a non-aqueous electrolyte; a first current collecting portion electrically connected to the first current collector; Equipped with the first electrode, the second electrode, and the separator form a columnar wound body, one end portion along the longitudinal direction of the first current collector is a first exposed portion that does not have the first active material layer and protrudes from one end face of the wound body, the first current collecting portion has a porous metal portion and one or more protrusions press-fitted into the porous metal portion, the porous metal portion is in contact with the first exposed portion, the first current collecting portion includes a first current collecting plate, The protrusion protrudes from the first current collector plate, The protrusion has a through-hole that penetrates the first current collector plate.

2. The power storage device according to claim 1 , wherein the porous metal portion is an aggregate of a plurality of metal particles.

3. The power storage device according to claim 1 , wherein the protrusion protrudes from a bottom of a bottomed case that houses the first electrode, the second electrode, the separator, and the non-aqueous electrolyte.

4. The power storage device according to any one of claims 1 to 3, wherein the tip of the protrusion is hook-shaped.

5. The power storage device according to any one of claims 1 to 4, wherein the first exposed portion is folded back at least once.

6. At least a portion of the first exposed portion is subdivided by a plurality of slits extending in the short-side direction of the first current collector. The electricity storage device according to any one of claims 1 to 5.

7. The porous metal portion is formed intermittently in the winding direction of the first exposed portion. The electricity storage device according to any one of claims 1 to 6.

8. A first electrode comprising a long sheet-like first current collector and a first active material layer supported on the first current collector; a second electrode in the form of a long sheet; a separator interposed between the first electrode and the second electrode; a non-aqueous electrolyte; a first current collecting portion electrically connected to the first current collector; Equipped with the first electrode, the second electrode, and the separator form a columnar wound body, one end portion along the longitudinal direction of the first current collector is a first exposed portion that does not have the first active material layer and protrudes from one end face of the wound body, the first current collecting portion has a porous metal portion and one or more protrusions press-fitted into the porous metal portion, the porous metal portion is in contact with the first exposed portion, The porous metal portion is formed intermittently in the winding direction of the first exposed portion.

9. Some of the porous metal portions arranged in the winding direction at predetermined intervals are overlapped with each other and arranged in the radial direction of the winding body on the end surface of the winding body. The electricity storage device according to claim 7 or 8.

10. preparing a first electrode comprising a long sheet-like first current collector and a first active material layer carried on the first current collector, wherein one end of the first current collector along a longitudinal direction is a first exposed portion that does not have the first active material layer; preparing a second electrode in the form of a long sheet; preparing a separator to be interposed between the first electrode and the second electrode; forming a columnar wound body from the first electrode, the second electrode, and the separator, and causing the first exposed portion to protrude from one end surface of the wound body; applying a conductive paste containing metal particles to the first exposed portion and solidifying or curing the conductive paste to form a porous metal portion that fills the gaps in the first exposed portion; and a step of press-fitting one or more protrusions into the porous metal portion to form a first current collecting portion.

11. The step of applying the conductive paste to the first exposed portion includes:

11. The method for manufacturing an electricity storage device according to claim 10, comprising: winding the first electrode and the second electrode with the separator interposed therebetween while applying the conductive paste to the one end of the first electrode before being wound.

12. the one end of the first electrode is folded back at least once before the conductive paste is applied to the one end of the first electrode; The method for manufacturing the electricity storage device according to claim 11 .

13. The step of applying the conductive paste to the first exposed portion includes:

11. The method for manufacturing an electricity storage device according to claim 10, comprising: preparing a first current collector plate having the protruding protrusion; applying the conductive paste to the surface of the first current collector plate from which the protrusion protrudes to form a coating film; and arranging the first current collector plate on the one end surface of the wound body with the coating film interposed therebetween.

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