Stacked secondary battery

Abstract

To keep the interface resistance low even when current collecting foils are joined together via a resin layer.SOLUTION: A battery includes a plurality of units in a stacking direction, each unit having a structure in which a positive electrode active material layer and a negative electrode active material layer are stacked with an electrolyte layer interposed between a pair of current collecting foils. At least the current collecting foil facing an adjacent unit of the pair of current collecting foils includes a conductive protrusion and is electrically connected to the current collecting foil in the adjacent unit via the conductive protrusion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a stacked secondary battery. [Background technology]

[0002] Some laminated secondary batteries include multiple units each formed by stacking a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer (including a separator layer in the case of a liquid electrolyte) between a pair of current collector foils. In this case, adjacent units face each other across the current collector foil. Therefore, in order to manufacture such a laminated secondary battery, a technique is employed in which opposing current collector foils are bonded together.

[0003] For example, Patent Document 1 discloses a solid-state battery comprising multiple stacked solid-state battery cells, each including a solid electrolyte layer between a positive electrode active material layer and a negative electrode active material layer, a positive electrode current collector on the surface of the positive electrode active material layer opposite the surface that contacts the solid electrolyte layer, and a negative electrode current collector on the surface of the negative electrode active material layer opposite the surface that contacts the solid electrolyte layer. In the solid-state battery disclosed in Patent Document 1, when stacking the solid-state battery cells, the positive electrode current collectors or negative electrode current collectors of adjacent solid-state battery cells are bonded together. Patent Document 1 claims that roughening one of the positive electrode current collectors or negative electrode current collectors to be bonded increases the coefficient of friction and prevents misalignment or rotation of the stacked positions. Patent Document 1 also claims that providing a conductive layer (carbon coating layer) with a high coefficient of friction on the surface when bonding the positive electrode current collectors or negative electrode current collectors can prevent misalignment or rotation of the stacked positions.

[0004] Furthermore, Patent Document 2 discloses that in a stacked secondary battery, a large number of current collector foils and current collector terminals are joined together by an ultrasonic joining method. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 181097 [Patent Document 2] Patent Publication No. 2021-16878 Summary of the Invention [Problem to be solved by the invention]

[0006] In stacked secondary batteries in which current collecting foils are bonded together, the current collecting foils are bonded together using a carbon coating layer or adhesive layer disposed between the current collecting foils. However, bonding current collecting foils together using a carbon coating layer or adhesive layer in stacked secondary batteries poses the problem of increased interfacial resistance between the current collecting foils.

[0007] In view of the above problems with stacked secondary batteries, the present disclosure aims to provide a stacked secondary battery that can keep interface resistance low even when current collecting foils are joined together via a resin layer. [Means for solving the problem]

[0008] The present disclosure, which achieves the above-mentioned objectives, includes the following. <1> a plurality of units in the stacking direction, each unit having a structure in which a positive electrode active material layer and a negative electrode active material layer are stacked with an electrolyte layer interposed therebetween and disposed between a pair of current collecting foils; a stacked secondary battery, wherein at least one of the pair of current collecting foils that faces an adjacent unit has a conductive protrusion and is electrically connected to the current collecting foil in the adjacent unit via the conductive protrusion. <2> A first positive electrode active material layer, a first electrolyte layer, a first negative electrode active material layer, a negative electrode current collecting foil, a second negative electrode active material layer, a second electrolyte layer, and a second positive electrode active material layer are arranged in this order between the pair of current collecting foils of the unit, and one of the pair of current collecting foils is in contact with the first positive electrode active material layer, and the other of the pair of current collecting foils is in contact with the second positive electrode active material layer. <1> The stacked secondary battery according to claim 1. <3> A resin layer is disposed between the adjacent units, and the conductive protrusions penetrate the resin layer. <1> or <2> The stacked secondary battery according to claim 1. <4> The pair of current collecting foils have the conductive protrusions on one surface and a resin layer on the other surface. <1> ~ <3> 10. The stacked secondary battery according to claim 9, wherein the first electrode is a conductor. <5> One of the pair of current collecting foils has the conductive protrusions on at least one surface, and the other of the pair of current collecting foils has a resin layer on at least one surface. <1> ~ <4> 10. The stacked secondary battery according to claim 9, wherein the first electrode is a conductor. <6> The resin layer contains a carbon-based conductive material. <3> ~ <5> 10. The stacked secondary battery according to claim 9, wherein the first electrode is a conductor.

[0009] <7> a plurality of units in the stacking direction, each unit having a structure in which a positive electrode active material layer and a negative electrode active material layer are stacked with an electrolyte layer interposed therebetween and disposed between a pair of current collecting foils; an electrode stack, wherein at least one of the pair of current collecting foils facing an adjacent unit has a conductive protrusion and is electrically connected to the current collecting foil in the adjacent unit via the conductive protrusion. <8> A first positive electrode active material layer, a first electrolyte layer, a first negative electrode active material layer, a negative electrode current collecting foil, a second negative electrode active material layer, a second electrolyte layer, and a second positive electrode active material layer are arranged in this order between the pair of current collecting foils of the unit, and one of the pair of current collecting foils is in contact with the first positive electrode active material layer, and the other of the pair of current collecting foils is in contact with the second positive electrode active material layer. <7> The electrode stack according to claim 1. <9> A resin layer is disposed between the adjacent units, and the conductive protrusions penetrate the resin layer. <7> or <8> The electrode stack according to claim 1. <10> The pair of current collecting foils have the conductive protrusions on one surface and a resin layer on the other surface. <7> ~ <9> 10. The electrode stack according to claim 9, wherein the electrode stack is a laminate of a first electrode and a second electrode. <11> One of the pair of current collecting foils has the conductive protrusions on at least one surface, and the other of the pair of current collecting foils has a resin layer on at least one surface. <7> ~ <10> 10. The electrode stack according to claim 9, wherein the electrode stack is a laminate of a first electrode and a second electrode. <12> The resin layer contains a carbon-based conductive material. <9> ~ <11> 10. The electrode stack according to claim 9, wherein the electrode stack is a laminate of a first electrode and a second electrode.

[0010] <13> a positive electrode active material layer, a negative electrode active material layer, an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, a positive electrode current collector foil connected to the positive electrode active material layer, a negative electrode current collector foil connected to the negative electrode active material layer, a positive electrode terminal connected to the positive electrode current collector foil, and a negative electrode terminal connected to the negative electrode current collector foil; The positive electrode current collector foil and / or the negative electrode current collector foil have conductive protrusions and are electrically connected to the positive electrode terminal and / or the negative electrode terminal via the conductive protrusions. <14> A resin layer is disposed between the positive electrode current collector foil and the positive electrode terminal, and between the negative electrode current collector foil and the negative electrode terminal, and the conductive protrusions penetrate the resin layers. <13> The secondary battery according to claim 1. <15> The resin layer contains a carbon-based conductive material. <13> or <14> The secondary battery according to claim 1. [Effects of the Invention]

[0011] According to the present disclosure, even in a stacked secondary battery in which current collectors are joined together via a resin layer, it is possible to keep the interface resistance low. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of a main portion schematically showing a stacked electrode assembly in a stacked secondary battery according to the present disclosure. [Figure 2A] 1 is a cross-sectional view schematically illustrating a main portion of a current collector foil shown as one embodiment of a stacked secondary battery according to the present disclosure. [Figure 2B] 2B is a cross-sectional view of a main part that schematically shows an electrode body that is stacked using the current collecting foil shown in FIG. 2A. FIG. [Figure 3A] FIG. 3 is a cross-sectional view schematically illustrating a main portion of a current collector foil shown as another embodiment of the stacked secondary battery of the present disclosure. [Figure 3B] 3B is a cross-sectional view of a main part that schematically shows an electrode body that is stacked using the current collecting foil shown in FIG. 3A. FIG. [Figure 4A] FIG. 4 is a cross-sectional view schematically illustrating a main portion of a current collector foil shown as still another embodiment of the stacked secondary battery of the present disclosure. [Figure 4B]4B is a cross-sectional view of a main part that schematically shows an electrode body that is stacked using the current collecting foil shown in FIG. 4A. FIG. [Figure 5A] FIG. 4 is a cross-sectional view schematically illustrating a main portion of a current collector foil shown as still another embodiment of the stacked secondary battery of the present disclosure. [Figure 5B] 5B is a cross-sectional view of a main part that schematically shows an electrode body that is stacked using the current collecting foils shown in FIG. 5A. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described. The description is for illustrating the embodiments and is not intended to limit the scope of the present disclosure.

[0014] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0015] In this specification, when an embodiment is described with reference to drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of components in each drawing are conceptual, and the relative size relationships between components are not limited to these.

[0016] The stacked secondary battery of the present disclosure has a plurality of units in the stacking direction, each unit having a structure in which a positive electrode active material layer and a negative electrode active material layer are stacked with an electrolyte layer interposed between them, and at least one of the pair of current collector foils that faces an adjacent unit has a conductive protrusion and is electrically connected to the current collector foil in the adjacent unit via the conductive protrusion. In the stacked secondary battery of the present disclosure, the conductive protrusion electrically connects the current collector foils in adjacent units, making it possible to keep the interface resistance between the current collector foils low.

[0017] One embodiment of the stacked secondary battery of the present disclosure will be described below with reference to the drawings. As shown in Fig. 1, the stacked secondary battery 1 shown as one embodiment has a first positive electrode active material layer 3A, a first electrolyte layer 5A, a first negative electrode active material layer 4A, a negative electrode current collector foil 6, a second negative electrode active material layer 4B, a second electrolyte layer 5B, and a second positive electrode active material layer 3B arranged in this order between a current collector foil 2A and a current collector foil 2B, with the pair of current collector foils 2A in contact with the first positive electrode active material layer 3A and the pair of current collector foils 2B in contact with the second positive electrode active material layer 3B. In the stacked secondary battery 1 shown in Fig. 1, the current collector foil 2A and the current collector foil 2B function as positive electrode current collectors.

[0018] In the following description, the first positive electrode active material layer 3A and the second positive electrode active material layer 3B are collectively referred to as the positive electrode active material layer 3, and other members with reference numerals "A" and "B" are also referred to in the same manner.

[0019] In the laminated secondary battery 1, negative electrode active material layers 4 are provided on both sides of a negative electrode current collector foil 6, and each of these negative electrode active material layers 4 faces a positive electrode active material layer 2 with an electrolyte layer 5 interposed therebetween. Therefore, the laminated secondary battery 1 has two structures, each of which has a positive electrode active material layer 3 and a negative electrode active material layer 4 laminated with an electrolyte layer 5 interposed between the current collector foil 2A and the current collector foil 2B. Hereinafter, the current collector foil 2A and the current collector foil 2B, and a laminate structure having two structures, each of which has a positive electrode active material layer 3 and a negative electrode active material layer 4 laminated with an electrolyte layer 5 interposed between the current collector foil 2A and the current collector foil 2B, will be referred to as a unit.

[0020] The laminated secondary battery 1 includes multiple units stacked in the stacking direction (the direction of arrow X in FIG. 1 ) of current collector foils 2A and 2B, positive electrode active material layers 3, negative electrode active material layers 4, electrolyte layers 5, and negative electrode current collector foils 6, with resin layers 7 provided between each unit. The resin layers 7 join the current collector foils 2A and 2B of adjacent units, but may also be disposed on the outer side of the units (current collector foils 2A or 2B) located at both ends of the laminated structure. Furthermore, the laminated secondary battery 1 may not have resin layers 7 on the outer side of the units (current collector foils 2A or 2B) located at both ends of the laminated structure. The number of units stacked with resin layers 7 interposed therebetween in the laminated secondary battery 1 is not particularly limited, and may be, for example, 10, 20, 30, 40, 50, 60, 70, 80, or more.

[0021] In the stacked secondary battery 1, the current collector foils 2A and 2B, which function as positive electrode current collectors, are elongated in a direction (arrow Y in FIG. 1) perpendicular to the stacking direction (arrow X in FIG. 1) beyond the positive electrode active material layer 3, the negative electrode active material layer 4, the electrolyte layer 5, and the negative electrode current collector foil 6. Although not shown in FIG. 1, the current collector foils 2A and 2B are overlapped at their elongated portions and connected to a positive electrode terminal (not shown). Similarly, the negative electrode current collector foil 6 is elongated in a direction (arrow Y in FIG. 1) opposite to the elongation direction of the current collector foils 2A and 2B beyond the current collector foils 2A and 2B, the positive electrode active material layer 3, the negative electrode active material layer 4, and the electrolyte layer 5. The elongated portions are overlapped and connected to a negative electrode terminal (not shown).

[0022] The laminated secondary battery 1 is provided with an insulating layer 8 that prevents short-circuiting between the current collector foil 2A and current collector foil 2B, which are attached to the positive electrode active material layer 3 and function as positive electrode current collectors, and the negative electrode active material layer 4, electrolyte layer 5, and negative electrode current collector foil 6. The insulating layer 8 is structured to cover the negative electrode active material layer 4, electrolyte layer 5, and negative electrode current collector foil 6 with the current collector foil 2A and current collector foil 2B of each unit overlapping at their extended portions.

[0023] [Cathode active material layer] The positive electrode active material contained in the positive electrode active material layer may be any known material. Examples of the positive electrode active material include LiCoO, lithium nickel-containing composite oxide, LiMnO, olivine-type lithium iron phosphate, TiS, MnO, MoO, and VO. The positive electrode active material may contain any one of these compounds alone or multiple types.

[0024] [Negative electrode active material layer] The negative electrode active material contained in the negative electrode active material layer is not particularly limited, and conventionally known materials can be used as appropriate. Examples of the negative electrode active material include carbon materials. Examples of carbon materials include cokes such as petroleum coke, pitch coke, and coal coke; carbon blacks such as carbides of organic compounds, carbon fiber, and acetylene black; and graphites such as artificial graphite and natural graphite. Other examples of the negative electrode active material include conductive polymers, lithium titanate, silicon, and silicon compounds. The above-mentioned materials may be used alone or in combination as the negative electrode active material.

[0025] [Negative electrode current collecting foil] The material constituting the negative electrode current collector foil is not particularly limited, and materials conventionally used in producing negative electrodes can be used. The material of the negative electrode current collector foil is not particularly limited, and examples thereof include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel, with Cu being particularly preferred. The negative electrode current collector foil can be in the form of a foil, a perforated foil, a mesh, or a strip.

[0026] [Current collecting foil and current collecting foil] The materials constituting the current collecting foil and the current collecting foil are not particularly limited, and materials conventionally used in producing positive electrodes can be used. The materials for the current collecting foil and the current collecting foil are not particularly limited, and examples thereof include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel, with Al being particularly preferred.

[0027] [Electrolyte layer] The electrolyte layer contains a solid electrolyte and / or a liquid electrolyte. When the electrolyte layer does not contain a solid electrolyte but contains a liquid electrolyte, the electrolyte layer may contain a separator to prevent short-circuiting between the positive electrode active material layer and the negative electrode active material layer. The solid electrolyte or liquid electrolyte is not particularly limited, and conventionally known materials can be used as appropriate.

[0028] [Resin layer] The resin constituting the resin layer is not particularly limited, and examples thereof include epoxy resin, acrylic resin, cyanoacrylate resin, polyurethane resin, silicone resin, phenolic resin, polyimide resin, vinyl resin, melamine resin, alkyd resin, etc. Furthermore, polyolefin resin and polyester resin into which a polar group has been introduced can also be used for the adhesive layer.

[0029] The resin layer 7 also bonds the current collector foil 2A and the current collector foil 2B, which are electrically connected by the conductive protrusions. Therefore, the resin layer does not need to be conductive, but may contain a conductive material. The resin layer containing a conductive material can further reduce the interfacial resistance between the current collector foil 2A and the current collector foil 2B. Examples of conductive materials contained in the resin layer 7 include, but are not limited to, cokes such as petroleum coke, pitch coke, and coal coke; carbides of organic compounds, carbon blacks such as carbon fiber and acetylene black; and carbon-based conductive materials such as artificial graphite and natural graphite.

[0030] In the stacked secondary battery 1 of the present disclosure, the current collector foils 2A and 2B in adjacent units are joined via the resin layer 7, and the current collector foils 2A and 2B are electrically connected by the conductive protrusions. Note that although the conductive protrusions are not shown in Fig. 1, various embodiments will be described with reference to Figs. 2A to 5B.

[0031] One embodiment of the present disclosure can be exemplified by a stacked secondary battery 1 using current collector foil 2A and current collector foil 2B, which have conductive protrusions 10 on at least one main surface thereof, as shown in Fig. 2A. That is, in the stacked secondary battery 1 shown in Fig. 1, current collector foil 2A and current collector foil 2B having conductive protrusions 10 on at least one main surface thereof are used. In this case, as shown in Fig. 2B, in the stacked secondary battery 1, at least one of current collector foil 2A and current collector foil 2B is arranged so that the conductive protrusions 10 face the side opposite to the surface in contact with positive electrode active material layer 3.

[0032] With this configuration, in the laminated secondary battery 1 of the present disclosure, the current collector foil 2A and the current collector foil 2B, which face each other with the resin layer 7 interposed therebetween, can be electrically connected by the conductive protrusions 10. Here, the conductive protrusions 10 are not particularly limited and can be formed by methods such as sandblasting, plating, or applying a resin containing a conductive filler to at least one surface of the current collector foil 2A and the current collector foil 2B. In addition, by appropriately setting the conditions for these methods, the height, in-plane density, etc. of the conductive protrusions 10 can be appropriately adjusted.

[0033] In the stacked secondary battery 1 of the present disclosure, the conductive protrusions 10 are preferably disposed between adjacent units and penetrate the resin layer 7 that joins the current collector foil 2A and the current collector foil 2B. This allows the conductive protrusions 10 to electrically connect the current collector foil 2A and the current collector foil 2B of the adjacent units. For the conductive protrusions 10 to penetrate the resin layer 7, the height of the conductive protrusions 10 may be greater than the thickness of the resin layer 7. The height of the conductive protrusions 10 may also be determined by the surface roughness Rz (referred to as the "maximum height"). Here, the surface roughness Rz is the maximum height roughness in accordance with JIS B0601 (2013). Specifically, the surface roughness Rz of the surfaces of the current collector foil 2A and the current collector foil 2B on which the conductive protrusions 10 are formed can be measured at any point on the surface using a laser microscope (Keyence, VK-X3000) as a measuring device, and the value obtained from the measurement can be used. By making the surface roughness Rz of the surface on which the conductive protrusions 10 are formed in the current collector foil 2A and / or the current collector foil 2B greater than the thickness of the resin layer 7, the conductive protrusions 10 can penetrate the resin layer 7 and electrically connect the current collector foil 2A and the current collector foil 2B of adjacent units.

[0034] The thickness of the resin layer 7 is preferably smaller than the height (i.e., Rz) of the conductive bumps 10. The film thickness of the resin layer 7 can be, for example, 95% or less, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 65% or less of the height (i.e., Rz) of the conductive bumps 10. By setting the upper limit of the film thickness of the resin layer 7 within this range, it is possible to ensure a reliable electrical connection between the current collector foil 2A and the current collector foil 2B. Specifically, the film thickness of the resin layer 7 is preferably 1 μm to 10 μm, and more preferably 1 μm to 5 μm.

[0035] In the embodiment shown in Figures 2A and 2B, since the conductive protrusions 10 can electrically connect the current collector foil 2A and the current collector foil 2B, the resin layer 7 may or may not be conductive.

[0036] 3A, current collecting foils 2A and 2B having conductive protrusions 10 on one main surface are used, and resin layers 7 are disposed in advance on the other main surfaces of current collecting foils 2A and 2B. In this case, as shown in FIG. 3B, in stacked secondary battery 1, current collecting foil 2A is disposed so that conductive protrusions 10 face the side opposite to the surface in contact with positive electrode active material layer 3, and current collecting foil 2B is disposed so that resin layer 7 faces the side opposite to the surface in contact with positive electrode active material layer 3. By disposing current collecting foils 2A and 2B in this manner, current collecting foils 2A and 2B facing each other with resin layer 7 interposed therebetween can be electrically connected by conductive protrusions 10.

[0037] In the embodiment shown in Figures 3A and 3B, since the conductive protrusions 10 can electrically connect the current collector foil 2A and the current collector foil 2B, the resin layer 7 may or may not be conductive.

[0038] In another embodiment of the present disclosure, as shown in FIG. 4A , one of the current collector foils 2A and 2B (conveniently referred to as current collector foil 2A) has conductive protrusions 10 on at least one main surface. In this embodiment, the other of the current collector foils 2A and 2B (conveniently referred to as current collector foil 2B) does not have conductive protrusions 10, but has a resin layer 7 previously disposed on at least one surface, as shown in FIG. 4A . In this case, as shown in FIG. 4B , the current collector foil 2A having conductive protrusions 10 is disposed so that the conductive protrusions 10 face the side opposite to the side in contact with the positive electrode active material layer 3. Furthermore, as shown in FIG. 4B , the current collector foil 2B having the resin layer 7 disposed thereon is disposed so that the resin layer 7 faces the side opposite to the side in contact with the positive electrode active material layer 3. With this configuration, in the laminate-type secondary battery 1 of the present disclosure, the current collector foils 2A and 2B, which face each other with the resin layer 7 interposed therebetween, can be electrically connected by the conductive protrusions 10.

[0039] In the embodiment shown in Figures 4A and 4B, since the conductive protrusions 10 can electrically connect the current collector foil 2A and the current collector foil 2B, the resin layer 7 may or may not be conductive.

[0040] In yet another embodiment of the present disclosure, as shown in FIG. 5A , one of the current collector foils 2A and 2B (conveniently referred to as current collector foil 2A) has conductive protrusions 10 on at least one main surface. In this embodiment, the other of the current collector foils 2A and 2B (conveniently referred to as current collector foil 2B) does not have conductive protrusions 10, but has resin layers 7 pre-formed on both surfaces, as shown in FIG. 5A . In this case, as shown in FIG. 5B , the current collector foil 2A having conductive protrusions 10 is arranged so that the conductive protrusions 10 face the side opposite the surface in contact with the positive electrode active material layer 3. In this case, the current collector foil 2B having resin layers 7 on both surfaces can be arranged regardless of whether it is front or back. This configuration allows the current collector foil 2A and the current collector foil 2B, which face each other with the resin layer 7 interposed therebetween, to be electrically connected by the conductive protrusions 10 in the laminated secondary battery 1 of the present disclosure.

[0041] 5A and 5B, the conductive protrusions 10 can electrically connect the current collector foil 2A and the current collector foil 2B, but the current collector foil 2B, which has resin layers 7 on both sides, must be electrically connected to the positive electrode active material layer 3. Therefore, in this case, a conductive resin layer 7 is used.

[0042] As described above, in the stacked secondary battery 1 of the present disclosure, the current collector foils 2A and 2B in adjacent units can be electrically connected by the conductive protrusions 10 arranged on at least one surface of the current collector foil 2A and / or the current collector foil 2B, thereby keeping the interface resistance between the current collector foils 2A and 2B in adjacent units low.

[0043] Furthermore, in the stacked secondary battery 1 of the present disclosure, as described above, the current collector foils 2A and 2B are overlapped at their extended portions and connected to a positive electrode terminal (not shown). At this time, the contact portions between the current collector foils 2A and 2B and the positive electrode terminal can be electrically connected via conductive protrusions 10, as in the configurations shown in FIGS. 2A to 5B. In this case, in the stacked secondary battery 1 of the present disclosure, the interface resistance between the current collector foils 2A and 2B in adjacent units can be kept low, and further, the interface resistance between the positive electrode terminal and the current collector foils 2A and 2B can also be kept low.

[0044] 1 to 5B , the laminated secondary battery of the present disclosure may include a positive electrode active material layer, a negative electrode active material layer, an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, a positive electrode current collector foil connected to the positive electrode active material layer, a negative electrode current collector foil connected to the negative electrode active material layer, a positive electrode terminal connected to the positive electrode current collector foil, and a negative electrode terminal connected to the negative electrode current collector foil, wherein the positive electrode current collector foil and / or the negative electrode current collector foil have conductive protrusions and are electrically connected to the positive electrode terminal and / or the negative electrode terminal via the conductive protrusions. In this case, the laminated secondary battery of the present disclosure may electrically connect the positive electrode current collector foil and the positive electrode terminal and / or the negative electrode current collector foil and the negative electrode terminal via the conductive protrusions. In this case, in the laminated secondary battery of the present disclosure, the interface resistance between the positive electrode current collector foil and the positive electrode terminal and / or the interface resistance between the negative electrode current collector foil and the negative electrode terminal can be kept low.

[0045] In this case, the positive electrode current collector foil and the positive electrode terminal and / or the negative electrode current collector foil and the negative electrode terminal can be electrically connected by combining conductive protrusions and a resin layer, as in the configurations shown in Figures 2A to 5B above. That is, a resin layer may be disposed between the positive electrode current collector foil and the positive electrode terminal and / or between the negative electrode current collector foil and the negative electrode terminal, and the conductive protrusions formed on the positive electrode current collector foil and / or the negative electrode current collector foil may penetrate the resin layer. [Example]

[0046] The present disclosure will be described in more detail below using examples, but the technical scope of the present disclosure is not limited to the following examples.

[0047] [Example 1] 1. Fabrication of stacked secondary batteries 1.1. Preparation of the positive electrode First, using a rolling fluidized coating device (manufactured by Powrex Corporation), positive electrode active material particles (Li 1.15 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 Lithium niobate was coated onto particles (with a main phase of O2) and then fired in an air atmosphere to obtain positive electrode active material particles having a lithium niobate coating layer. Next, polyvinylidene fluoride (PVdF), the positive electrode active material particles, a sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), and vapor-grown carbon fiber (VGCF, manufactured by Resonac Corporation) were placed in a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50 manufactured by SMT Corporation). Next, the container was shaken for 3 minutes using a shaker (TTM-1 manufactured by Shibata Scientific Co., Ltd.) and further stirred for 30 seconds using the ultrasonic disperser. After shaking for 3 minutes using the shaker, the resulting slurry was applied to aluminum foil using an applicator by the blade method. The mixture was then air-dried and then dried on a hot plate at 100 °C for 30 minutes to obtain a positive electrode having a positive electrode active material layer on the aluminum foil.

[0048] 1.2. Preparation of the negative electrode PVdF, negative electrode active material particles (lithium titanate, LTO particles), and the sulfide solid electrolyte used in the positive electrode were placed in a polypropylene container and stirred for 30 minutes using an ultrasonic disperser. The resulting slurry was applied to copper foil using an applicator blade method. The resulting mixture was then air-dried and then dried on a hot plate at 100°C for 30 minutes to obtain a negative electrode having a negative electrode active material layer on the copper foil (negative electrode current collector foil). The reverse side of the copper foil was then similarly coated with the slurry and dried.

[0049] 1.3. Preparation of electrolyte layer Heptane, butadiene rubber (BR), and the sulfide solid electrolyte used in the positive electrode were added to a polypropylene container and stirred for 30 seconds using an ultrasonic disperser. The container was then shaken for 30 minutes using a shaker (Shibata Scientific TTM-1) and further stirred for 30 seconds using the ultrasonic disperser. After shaking for 3 minutes using the shaker, the resulting slurry was applied to aluminum foil using an applicator by the blade method. The resulting mixture was then air-dried and then dried on a hot plate at 100°C for 30 minutes to form an electrolyte layer containing the solid electrolyte on the aluminum foil substrate.

[0050] 1.4. Preparation of resin layer The conductive materials acetylene black and PVdF were weighed out to 20% by mass and 80% by mass, respectively, with the total being 100% by mass. N-methylpyrrolidone was then added to prepare a conductive carbon-coated resin composition. Next, the composition was coated on one side of an aluminum foil to a thickness of 2 μm, and dried at 100° C. for 1 hour to prepare a conductive resin layer on the aluminum foil.

[0051] 1.5. Preparation of electrode body First, the negative electrode active material layers on both sides of the negative electrode prepared in 1.2. were attached to the electrolyte layers prepared in 1.3. in a direction in which they were in direct contact, and pressed at 1.6 t / cm. The aluminum foil substrate was then peeled off from the electrolyte layers. Next, the positive electrode active material layers and the electrolyte layers were attached (both sides) in direct contact, and pressed at 1.6 t / cm. The aluminum foil was then peeled off, and the positive electrode active material layer was cut to 70 mm x 70 mm. Next, an insulating layer made of polyimide was attached to the positive electrode active material layer. After that, a first current collector foil (a conductive resin layer on the aluminum foil obtained in 1.4) was attached to one of the positive electrode active material layers, and a second current collector foil (roughened nickel foil) was attached to the other positive electrode active material layer, and the resulting foil was densified at 5 t / cm. The resulting foil was then cut into a tab shape to prepare an electrode body. The roughened nickel foil used had an Rz of 4 μm.

[0052] 1.6. Fabrication of stacked secondary batteries Seventy electrode assemblies prepared in 1.5 were stacked. The first and second current collector foils extending from one end of the electrode assembly were overlapped with a positive electrode terminal and pressed at 140°C and 5 MPa to bond them. The negative electrode current collector foil extending from the other end of the electrode assembly was overlapped with a negative electrode terminal and ultrasonic bonding was performed. The 70 stacked electrode assemblies were then laminate-sealed to obtain a stack-type secondary battery.

[0053] Evaluation The resistance of the resulting stacked secondary battery was measured. First, it was CCCV charged to 2.95 V at 0.3 C, and then discharged to 1.5 V. Then, it was charged to 2.17 V and CC discharged at 5 C, and the resistance was calculated from ΔV.

[0054] [Comparative Example 1] A stacked secondary battery was fabricated in the same manner as in Example 1, except that a roughened nickel foil with an Rz of 1 μm was used as the second current collector foil, and the resistance was measured. Comparative Example 2 A stacked secondary battery was fabricated in the same manner as in Example 1, except that a nickel foil with an Rz of 0.1 μm was used as the second current collector foil, and the resistance was measured. Comparative Example 3 A stacked secondary battery was fabricated in the same manner as in Example 1, except that a roughened nickel foil with an Rz of 4 μm was used for the first current collector foil and the second current collector foil, and the resistance was measured. Comparative Example 4 A stacked secondary battery was attempted in the same manner as in Example 1, except that the aluminum foil (without the resin layer) used in producing the resin layer was used as the first current collecting foil, nickel foil was used as the second current collecting foil, and 70 electrode bodies were stacked by ultrasonic bonding.

[0055] <<Results>> The resistances measured for the stacked secondary batteries fabricated in Example 1 and Comparative Examples 1 to 3 are shown in Table 1. In Comparative Example 4, foil breakage occurred, and a stacked secondary battery could not be fabricated.

[0056] [Table 1]

[0057] As shown in Table 1, compared to Comparative Examples 1 to 3, in the stacked secondary battery produced in Example 1, by using a current collector foil with conductive convex portions formed thereon, adjacent electrode bodies were electrically connected and the resistance value was able to be kept low. [Reference Experimental Example] The roughened nickel foil having an Rz of 4 μm used in Example 1 and the roughened nickel foil having an Rz of 1 μm used in Comparative Example 2 were bonded to the carbon-coated aluminum foil used in Example 1, etc., and then mechanically peeled off, and the peeled surface of the carbon-coated aluminum foil was observed. As a result, although not shown, when the roughened nickel foil having an Rz of 4 μm used in Example 1 was bonded, it was found that the conductive convex portions formed on the roughened nickel foil formed many holes on the peeled surface that penetrated the carbon coating layer and reached the aluminum foil. In contrast, when the roughened nickel foil having an Rz of 1 μm used in Comparative Example 2 was used, no holes were observed that penetrated the carbon coating layer and reached the aluminum foil. [Explanation of symbols]

[0058] 1... laminated secondary battery, 2A, 2B... current collecting foil, 3... positive electrode active material layer, 4... negative electrode active material layer, 5... electrolyte layer, 6... negative electrode current collecting foil, 7... resin layer, 8... insulating layer, 10... conductive protrusion

Claims

1. a plurality of units in the stacking direction, each unit having a structure in which a positive electrode active material layer and a negative electrode active material layer are stacked with an electrolyte layer interposed therebetween and disposed between a pair of current collecting foils; a stacked secondary battery, wherein at least one of the pair of current collecting foils that faces an adjacent unit has a conductive protrusion and is electrically connected to the current collecting foil in the adjacent unit via the conductive protrusion.

2. 2. The stack-type secondary battery according to claim 1, wherein a first positive electrode active material layer, a first electrolyte layer, a first negative electrode active material layer, a negative electrode current collector foil, a second negative electrode active material layer, a second electrolyte layer, and a second positive electrode active material layer are arranged in this order between the pair of current collector foils of the unit, one of the pair of current collector foils being in contact with the first positive electrode active material layer, and the other of the pair of current collector foils being in contact with the second positive electrode active material layer.

3. 2. The stacked secondary battery according to claim 1, wherein a resin layer is disposed between adjacent ones of the units, and the conductive protrusions penetrate the resin layer.

4. 2. The stacked secondary battery according to claim 1, wherein each of the pair of current collector foils has the conductive protrusions on one surface and a resin layer on the other surface.

5. 2. The stacked secondary battery according to claim 1, wherein one of the pair of current collector foils has the conductive protrusions on at least one surface, and the other of the pair of current collector foils has a resin layer on at least one surface.

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