Current collector

Abstract

To increase conductivity of a current collector.SOLUTION: The present invention is composed of a metal or alloy powder and an electroless plating layer covering the metal or alloy powder, and the conductivity of the metal or alloy powder and that of the plating layer are the same or the conductivity of the metal or alloy powder is larger than that of the plating layer.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a current collector. [Background technology]

[0002] In recent years, there has been a strong desire to reduce carbon dioxide emissions in order to combat global warming. The automotive industry is hoping that the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs) will help reduce carbon dioxide emissions, and there has been active development of non-aqueous electrolyte secondary batteries, such as secondary batteries for driving motors, which hold the key to putting these vehicles into practical use.

[0003] Secondary batteries for driving motors are required to have extremely high output characteristics and high energy compared to consumer lithium-ion secondary batteries used in mobile phones, laptops, etc. Therefore, lithium-ion secondary batteries, which have the highest theoretical energy of all practical batteries, have attracted attention and are currently being rapidly developed.

[0004] In the currently widely used lithium ion secondary batteries, the electrodes are formed by applying a positive or negative electrode active material, etc. to a positive or negative electrode current collector using a binder. In the case of a bipolar battery, a bipolar electrode is formed by applying a positive electrode active material, etc. to one side of a current collector using a binder to form a positive electrode layer, and applying a negative electrode active material, etc. to the opposite side using a binder to form a negative electrode layer.

[0005] In such lithium-ion batteries, metal foils have conventionally been used as current collectors. One technique for such current collectors is disclosed in Patent Document 1, which discloses a current collector made of sintered iron-based powder, with a porosity of 30 to 55% by volume, and with a conductive metal layer on at least a portion of the inner circumferential surface of the pores. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-22254 Summary of the Invention [Problem to be solved by the invention]

[0007] In the case of conventional current collectors, the base iron and the plated copper are a combination of materials with a large difference in ionization tendency, resulting in a displacement type of electroless plating, and because it is a displacement deposition, the reaction stops when the base metal's surface is covered by the metal precipitated from the solution, so only a thin plating can be formed. Furthermore, the conductivity of the iron-based particles is about 1 / 6 that of the copper in the plated layer, so electricity flows only through the copper parts. In such cases, electrons move in a way that bypasses the iron-based powder, resulting in high electrical resistance.

[0008] The present invention aims to increase the conductivity of the current collector. [Means for solving the problem]

[0009] One aspect of the present invention that achieves the above object is a current collector that is composed of a metal or alloy powder and an electroless plating layer that covers the metal or alloy powder, and in which the conductivity of the metal or alloy powder and the plating layer are approximately the same or the conductivity of the metal or alloy powder is greater than the conductivity of the plating layer. [Effects of the Invention]

[0010] According to the current collector of the present invention, the conductivity of the current collector can be increased. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a secondary battery according to an embodiment; [Figure 2] FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. [Figure 3] FIG. 2 is a schematic diagram illustrating a current collector according to an embodiment. [Figure 4] 1A to 1C are schematic diagrams illustrating a method for producing a current collector according to an embodiment. [Figure 5]1A to 1C are schematic diagrams illustrating a method for producing a current collector according to an embodiment. [Figure 6] 1A to 1C are schematic diagrams illustrating a method for producing a current collector according to an embodiment. [Figure 7] 1A to 1C are schematic diagrams illustrating a method for producing a current collector according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] One embodiment of the present invention is a lithium secondary battery in which a power generating element including a positive electrode including a positive electrode active material layer containing a positive electrode active material, a negative electrode including a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer is encapsulated inside a battery exterior material.

[0013] The following describes the above-described embodiments of the present invention with reference to the drawings. However, the technical scope of the present invention should be defined based on the claims and is not limited to the following embodiments. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios. Below, the present invention will be described using a non-bipolar (internal parallel connection) flat-layered all-solid-state lithium secondary battery (hereinafter simply referred to as a "layered battery"), which is one type of secondary battery. As described above, the solid electrolyte constituting an all-solid-state lithium secondary battery is a material composed mainly of an ion conductor capable of ion conduction in a solid. Therefore, all-solid-state lithium secondary batteries have the advantage that, in principle, they do not encounter various problems associated with flammable organic electrolytes, as in conventional liquid-based lithium secondary batteries. Furthermore, generally, the use of a high-potential, high-capacity positive electrode material and a high-capacity negative electrode material has the advantage of significantly improving the output density and energy density of the battery.

[0014] Fig. 1 is a perspective view showing the appearance of a stacked battery according to one embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line 2-2 shown in Fig. 1. The stacked structure allows the battery to be compact and have a high capacity.

[0015] 1, stacked secondary battery 10a has a flat, rectangular shape, with a positive current collector 27 and a negative current collector 25 extending from both sides for extracting power. Power generating element 21 is wrapped in exterior body 29 (laminate film) of stacked secondary battery 10a, and the periphery is heat-sealed, with power generating element 21 sealed in a state in which positive current collector 27 and negative current collector 25 extend to the outside.

[0016] The all-solid-state battery according to this embodiment is not limited to a laminated, flat shape. A wound-type all-solid-state battery may be cylindrical, or may be a cylindrical battery modified to have a rectangular, flat shape, and is not particularly limited. The cylindrical battery may use a laminate film or a conventional cylindrical can (metal can) as its exterior material, and is not particularly limited. Preferably, the power generating element is housed inside a laminate film containing aluminum. This configuration can achieve weight reduction.

[0017] There are also no particular limitations on how the current collectors 27 and 25 shown in Fig. 1 are taken out. The positive current collector 27 and the negative current collector 25 may be taken out from the same side, or the positive current collector 27 and the negative current collector 25 may each be divided into multiple pieces and taken out from each side, and so on, without being limited to what is shown in Fig. 1. Furthermore, in a wound-type lithium-ion battery, terminals may be formed using, for example, a cylindrical can (metal can) instead of tabs.

[0018] As shown in FIG. 2, the stacked secondary battery 10a of this embodiment has a structure in which a flat, approximately rectangular power generating element 21, where charge and discharge reactions actually proceed, is sealed inside a laminate film that is an exterior body 29. Here, the power generating element 21 has a structure in which a positive electrode, a solid electrolyte layer 17, and a negative electrode are laminated. In this embodiment, the solid electrolyte layer 17 contains LPS (LiS-Ps), a type of sulfide solid electrolyte. The positive electrode has a structure in which a positive electrode active material layer 15 (corresponding to the second electrode layer) containing a positive electrode active material (here, elemental sulfur (S)) is disposed on both sides of a positive electrode current collector 11b (corresponding to the second current collector). The negative electrode has a structure in which a negative electrode active material layer 13 (corresponding to the first electrode layer) containing a negative electrode active material (here, an In-Li alloy) is disposed on both sides of a negative electrode current collector 11a (corresponding to the first current collector). Specifically, a positive electrode, a solid electrolyte layer, and a negative electrode are stacked in this order, with one positive electrode active material layer 15 and one negative electrode active material layer 13 facing each other with a solid electrolyte layer 17 interposed therebetween. The outer periphery of the negative electrode active material layer 13 constituting the negative electrode is surrounded by an insulating layer 12. As a result, adjacent positive electrodes, solid electrolyte layers, negative electrodes, and insulating layers constitute one unit cell layer 19 (corresponding to a battery section). Therefore, the stacked-type secondary battery 10a shown in FIG. 2 can be said to have a configuration in which a plurality of unit cell layers 19 are stacked and electrically connected in parallel. In this embodiment, an insulating layer 12 is disposed outside the surface of the negative electrode active material layer 13. In a plan view, the solid electrolyte layer 17 protrudes outward in the surface direction beyond the negative electrode active material layer 13. The negative electrode current collector 11a has the negative electrode active material layer 13 formed on its surface, and the positive electrode current collector 11b has the positive electrode active material layer 15 formed on its surface.

[0019] Positive electrode current collector 11b and negative electrode current collector 11a are respectively attached with positive electrode current collector (tab) 27 and negative electrode current collector (tab) 25 that are electrically connected to the respective electrodes (positive electrode and negative electrode), and are structured so as to be sandwiched between the ends of the laminate film that is outer casing 29 and led out of the laminate film. Positive electrode current collector 27 and negative electrode current collector 25 may be attached to positive electrode current collector 11b and negative electrode current collector 11a of the respective electrodes by ultrasonic welding, resistance welding, or the like, via positive electrode leads and negative electrode leads (not shown) as necessary.

[0020] The main components of the lithium secondary battery according to this embodiment will be described below.

[0021] [Current collector] The current collectors 11a and 11b function as a medium for transferring electrons from the electrode active material layer. There are no particular limitations on the material that constitutes the current collectors 11a and 11b. Examples of materials that can be used for the current collectors 11a and 11b include metals such as nickel, nickel-based and austenitic stainless steel, and alloy powders such as SUS316(L).

[0022] FIG. 3 is a schematic diagram showing current collectors 11a and 11b according to an embodiment. An electroless plating layer 11c can be formed on the outer surfaces of the metal particles of current collectors 11a and 11b. The conductivity of the metal or alloy powder and the plating layer 11c can be substantially the same or greater than that of the metal or alloy powder. This configuration allows electrons to flow through the powder and the plating layer 11c (see FIG. 3). Furthermore, compared to a simple plating layer, the addition of metal powder ensures a thicker plating layer 11c and provides greater conductivity (as measured by electrical conductivity, measured in units such as S / m). The plating solution used for the plating layer 11c can be an autocatalytic plating solution, such as an electroless copper plating solution. In addition to the autocatalytic plating solution, a displacement deposition plating solution can also be used. The plating layer 11c can have a thickness of, for example, 10-30 μm.

[0023] 4 to 7 are schematic diagrams illustrating a method for manufacturing a current collector according to an embodiment. Current collectors 11a and 11b can be manufactured by spreading metal powder on a substrate or the like, applying an autocatalytic electroless plating solution of the same type as the metal powder (metal particles 11d), drying, and then solidifying the metal powder through plating (see FIG. 4). In this case, the potential difference between the metal powder and the metal tube used for plating is small, so an autocatalytic precipitation reaction occurs, allowing a thick plating layer 11c to be formed. The drying process can be performed by blowing hot air for several tens of seconds to several minutes, for example, by moving a device in a parallel direction rather than directly applying hot air.

[0024] In addition, as a method for manufacturing the current collectors 11a and 11b, an inkjet method using the discharge unit 200 shown in Fig. 5 can be used to apply the electroless plating solution. By configuring in this way, the plating solution can be applied to a targeted position, and the shape of the current collector can be controlled.

[0025] In addition, current collectors 11a and 11b can be manufactured by mixing metal powder with the same type of autocatalytic electroless plating solution to form slurry 11e, which is then coated using coating unit 300 and dried and solidified using a dryer 400 or the like (see FIG. 6). Because the plating solution is autocatalytic electroless plating, a thick plating layer 11c can be formed. Furthermore, pores within the current collector can be reduced. Because plating layer 11c can be formed thick in this way, electrical conductivity can be improved, and because pores within the current collector are reduced, strength can also be improved.

[0026] As a method for producing the current collectors 11a and 11b, the metal powder of the current collectors 11a and 11b can be solidified and then roll-pressed using a roller 500 or the like as shown in Fig. 7. This densifies the inside of the current collector, thereby improving the energy density per volume of the battery.

[0027] Furthermore, the current collectors 11a and 11b are designed to be compatible with copper-based metal or alloy powder and electroless plating solution. This configuration allows for an autocatalytic reaction between the copper-based metal or alloy powder and the electroless plating solution, resulting in the formation of a thick plating film.

[0028] Furthermore, the specifications for the current collectors 11a and 11b allow for the use of an electroless nickel plating solution for nickel-based metal or alloy powder, which causes an autocatalytic reaction to occur, forming a thick plating film.

[0029] [Negative electrode (negative electrode active material layer)] In the secondary battery 10a according to this embodiment, the negative electrode active material layer 13 contains a lithium-containing negative electrode active material. Such a negative electrode active material absorbs lithium ions released from the positive electrode during charging and releases the lithium ions during discharging. The type of lithium-containing negative electrode active material is not particularly limited, but examples include metallic lithium and lithium-containing alloys. Examples of lithium-containing alloys include alloys of Li and at least one of Au, Ag, In, Al, Si, and Sn. In some cases, two or more types of negative electrode active materials may be used in combination.

[0030] The content of the negative electrode active material in the negative electrode active material layer 13 is not particularly limited, but is preferably within the range of 40 to 99 mass %, and more preferably within the range of 50 to 90 mass %, for example.

[0031] The negative electrode active material layer 13 preferably further includes a solid electrolyte. When the negative electrode active material layer 13 includes a solid electrolyte, the ionic conductivity of the negative electrode active material layer 13 can be improved. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, and a sulfide solid electrolyte is preferred.

[0032] Examples of sulfide solid electrolytes include LiI-Li2S-SiS2, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, LiI-Li3PS4, LiI-LiBr-Li3PS4, Li3PS4, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga, and In). The term "LiS-P2S5" refers to a sulfide solid electrolyte obtained using a raw material composition containing LiS and P2S5, and the same applies to other terms.

[0033] The sulfide solid electrolyte may have, for example, a Li3PS4 skeleton, a Li4P2S7 skeleton, or a Li4P2S6 skeleton. Examples of sulfide solid electrolytes having a Li3PS4 skeleton include LiI-Li3PS4, LiI-LiBr-Li3PS4, and Li3PS4. Examples of sulfide solid electrolytes having a Li4P2S7 skeleton include Li-PS-based solid electrolytes known as LPS (for example, Li7P3S 11 ) can be mentioned. In addition, examples of sulfide solid electrolytes include Li (4-x) Ge (1-x) P xAn LGPS or the like represented by S4 (where 0 < x < 1) may be used. Among them, the sulfide solid electrolyte contained in the active material layer is preferably a sulfide solid electrolyte containing P element, and more preferably a material mainly composed of Li2S - P2S5. Further, the sulfide solid electrolyte may contain halogen (F, Cl, Br, I). In a preferred embodiment, the sulfide solid electrolyte contains Li6PS5X (where X is Cl, Br or I, preferably Cl).

[0034] Also, when the sulfide solid electrolyte is of the Li2S - P2S5 system, the ratio of Li2S and P2S5 is preferably within the range of Li2S:P2S5 = 50:50 to 100:0 in molar ratio, and more preferably Li2S:P2S5 = 70:30 to 80:20.

[0035] Also, the sulfide solid electrolyte may be a sulfide glass, a crystallized sulfide glass, or a crystalline material obtained by a solid-phase method. The sulfide glass can be obtained, for example, by performing mechanical milling (such as a ball mill) on a raw material composition. Also, the crystallized sulfide glass can be obtained, for example, by heat-treating the sulfide glass at a temperature above the crystallization temperature. Also, the ionic conductivity (for example, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25 °C) is, for example, 1×10 -5 S / cm or more, preferably 1×10 -4 S / cm or more. The value of the ionic conductivity of the solid electrolyte can be measured by an alternating current impedance method.

[0036] Examples of the oxide solid electrolyte include compounds having a NASICON-type structure. As an example of a compound having a NASICON-type structure, a compound represented by the general formula Li 1+x Al x Ge 2-x (PO4)3 (0 ≦ x ≦ 2) (LAGP), a compound represented by the general formula Li 1+x Al x Ti 2-x(PO4)3 (0≦x≦2) (LATP) and the like. Another example of an oxide solid electrolyte is LiLaTiO (for example, Li 0.34 La 0.51 TiO3), LiPON (e.g., Li 2.9 PO 3.3 N 0.46 ), LiLaZrO (e.g., Li7La3Zr2O 12 ) etc.

[0037] The shape of the solid electrolyte may be, for example, a particulate shape such as a spherical shape or an oval spherical shape, or a thin film shape. When the solid electrolyte is particulate, its average particle diameter (D 50 ) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. 50 ) is preferably 0.01 μm or more, and more preferably 0.1 μm or more.

[0038] The content of the solid electrolyte in the negative electrode active material layer 13 is, for example, preferably in the range of 1 to 60 mass %, and more preferably in the range of 10 to 50 mass %.

[0039] The negative electrode active material layer 13 may further contain at least one of a conductive additive and a binder in addition to the above-mentioned negative electrode active material and solid electrolyte.

[0040] The thickness of the negative electrode active material layer 13 differs depending on the intended configuration of the secondary battery, but is preferably within the range of 0.1 to 1000 μm, for example.

[0041] [Solid electrolyte layer] In the secondary battery 10a according to this embodiment, the solid electrolyte layer 17 is interposed between the above-mentioned positive electrode active material layer 15 and negative electrode active material layer 13, and is a layer that essentially contains a solid electrolyte.

[0042] There are no particular restrictions on the specific form of the solid electrolyte contained in the solid electrolyte layer 17, and the solid electrolytes and their preferred forms exemplified in the section on the negative electrode active material layer 13 can be similarly employed. In some cases, a solid electrolyte other than the above-mentioned solid electrolytes may be used in combination. However, the content of the sulfide solid electrolyte relative to the total amount (100% by mass) of the solid electrolyte is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

[0043] The solid electrolyte layer 17 may further contain a binder in addition to the above-mentioned solid electrolyte.

[0044] The thickness of solid electrolyte layer 17 varies depending on the configuration of the intended lithium ion secondary battery, but from the viewpoint of improving the volumetric energy density of the battery, it is preferably 600 μm or less, more preferably 500 μm or less, and even more preferably 400 μm or less. On the other hand, there is no particular restriction on the lower limit of the thickness of solid electrolyte layer 17, but it is preferably 10 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more.

[0045] [Cathode active material layer] In the secondary battery 10a according to this embodiment, the positive electrode active material layer 15 contains a sulfur-containing positive electrode active material. The type of sulfur-containing positive electrode active material is not particularly limited, but examples include elemental sulfur (S) as well as particles or thin films of organic or inorganic sulfur compounds. Any material can be used as long as it utilizes the oxidation-reduction reaction of sulfur to release lithium ions during charging and absorb lithium ions during discharging. Examples of organic sulfur compounds include disulfide compounds, sulfur-modified polyacrylonitrile, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), and polycarbon sulfide, as typified by the compounds described in International Publication No. 2010 / 044437. Among these, disulfide compounds, sulfur-modified polyacrylonitrile, and rubeanic acid are preferred, with sulfur-modified polyacrylonitrile being particularly preferred. Disulfide compounds containing dithiobiurea derivatives, thiourea groups, thioisocyanates, or thioamide groups are more preferred. Here, sulfur-modified polyacrylonitrile is a modified polyacrylonitrile containing sulfur atoms, obtained by mixing sulfur powder with polyacrylonitrile and heating the mixture under an inert gas or under reduced pressure. Its estimated structure is, for example, as shown in Chem. Mater. 2011, 23, 5024-5028, in which polyacrylonitrile is ring-closed to form a polycyclic ring, and at least a part of S is bonded to C. The compound described in this document has a peak at 1330 cm in the Raman spectrum. -1 and 1560cm -1 There is a strong peak signal near 307 cm -1 , 379cm -1 , 472cm -1 , 929cm -1A peak is present around 0.05%. On the other hand, inorganic sulfur compounds are preferred due to their excellent stability. Specific examples include elemental sulfur (S), Li2S, TiS2, TiS3, TiS4, NiS, NiS2, CuS, FeS2, MoS2, and MoS3. Among these, S, Li2S, S-carbon composite, TiS2, TiS3, TiS4, FeS2, and MoS2 are preferred, with elemental sulfur (S), Li2S, TiS2, and FeS2 being more preferred. From the viewpoint of high capacity, elemental sulfur (S) or Li2S is particularly preferred. Note that, as elemental sulfur (S), α-sulfur, β-sulfur, or γ-sulfur having an S8 structure can be used. During discharge, these elemental sulfur (S) absorb lithium ions and exist in the positive electrode active material layer in the form of lithium (poly)sulfides.

[0046] In some cases, two or more kinds of positive electrode active materials may be used in combination. Of course, positive electrode active materials other than those mentioned above may also be used. However, the content of the sulfur-containing positive electrode active material in 100% by mass of the total amount of the positive electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

[0047] The content of the positive electrode active material in the positive electrode active material layer 15 is not particularly limited, but is preferably within the range of 35 to 99 mass %, and more preferably within the range of 40 to 90 mass %, for example.

[0048] The positive electrode active material layer 15 also preferably contains a solid electrolyte, and more preferably contains a sulfide solid electrolyte. Specific and preferred forms of the solid electrolyte, such as the sulfide solid electrolyte, may be the same as those described above in the section on the negative electrode active material layer 13. The positive electrode active material layer 15 may further contain a conductive additive and / or a binder.

[0049] [Positive and negative current collector plates] The material constituting the current collector plates 25, 27 is not particularly limited, and any known highly conductive material conventionally used as a current collector plate for a secondary battery can be used. Metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferred as the material constituting the current collector plates 25, 27. From the viewpoints of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferred, and aluminum is particularly preferred. The positive current collector plate 27 and the negative current collector plate 25 may be made of the same material or different materials.

[0050] [Positive and negative leads] Although not shown, the current collectors 11b and 11a may be electrically connected to the current collector plates 27 and 25 via positive and negative electrode leads. The materials used in known lithium-ion secondary batteries may be used as the constituent materials for the positive and negative electrode leads. The exposed portion is preferably covered with a heat-resistant, insulating heat-shrinkable tube or the like to prevent contact with peripheral devices or wiring, resulting in electrical leakage and affecting the product (e.g., automobile parts, particularly electronic devices).

[0051] [Exterior body] As the exterior body 29, a known metal can case can be used, or a bag-like case made of a laminate film containing aluminum can be used that can cover and store the cell layer 19 including the power generating element 21, as shown in Figures 1 and 2. The specific shape of the exterior body 29 is not particularly limited as long as it can store the cell layer 19 including the power generating element 21, etc., but the shape in a plan view can be a polygon such as a rectangle. An insulating coating can be provided on the surface of the exterior body 29.

[0052] [Insulating layer] Insulating layer 12 is formed around each electrode to prevent contact between adjacent current collectors 11b, 11a within the battery and to prevent short circuits due to slight misalignment of the edges of the stacked electrodes, etc. Polyolefin resins such as PE and PP, epoxy resins, rubber, polyimides, etc. can be used for insulating layer 12, and polyolefin resins are preferred from the standpoints of corrosion resistance, chemical resistance, film-forming properties, and economy, but the insulating layer is not limited to these.

[0053] The insulating layer 12 is formed so as to surround the outer periphery of the negative electrode active material layer 13 in a plan view.

[0054] Although one embodiment of the all-solid-state lithium secondary battery has been described above, the present invention is not limited to the configuration described in the above embodiment, and can be modified as appropriate based on the claims.

[0055] For example, in the all-solid-state lithium secondary battery according to the present embodiment, the solid electrolyte layer may further contain a conventionally known liquid electrolyte (electrolytic solution). There is no particular limitation on the amount of liquid electrolyte (electrolytic solution) that can be contained in the solid electrolyte layer, but it is preferably an amount that allows the shape of the solid electrolyte layer formed by the solid electrolyte to be maintained and prevents leakage of the liquid electrolyte (electrolytic solution).

[0056] [Battery pack] A battery pack is made up of multiple batteries connected together. Specifically, it is made up of at least two batteries connected in series, parallel, or both. By connecting them in series or parallel, it is possible to freely adjust the capacity and voltage.

[0057] A small, detachable assembled battery can be formed by connecting multiple batteries in series or in parallel. Furthermore, a large-capacity, high-output assembled battery (such as a battery module or battery pack) can be formed by further connecting multiple such small, detachable assembled batteries in series or in parallel, suitable for use as a vehicle drive power source or auxiliary power source, which require high volumetric energy density and high volumetric power density. The number of batteries to be connected to form a battery assembly and the number of stacked small assembled batteries to form a large-capacity assembled battery can be determined based on the battery capacity and output of the vehicle (electric vehicle) in which the battery will be installed.

[0058] [vehicle] A battery or a battery pack formed by combining a plurality of such batteries can be mounted on a vehicle. The present invention makes it possible to construct a long-life battery with excellent long-term reliability. Therefore, by incorporating such a battery, a plug-in hybrid electric vehicle with a long EV driving range or an electric vehicle with a long driving range per charge can be constructed. For example, a battery or a battery pack formed by combining a plurality of such batteries can be used in a hybrid vehicle, a fuel cell vehicle, or an electric vehicle (all of which include four-wheeled vehicles (commercial vehicles such as passenger cars, trucks, and buses, and light vehicles), as well as two-wheeled vehicles (motorcycles) and three-wheeled vehicles) to produce a vehicle with a long life and high reliability. However, the application is not limited to automobiles, and the battery pack can also be applied to various power sources for other vehicles, such as trains, and can also be used as an on-board power source for uninterruptible power supplies and the like.

[0059] The following embodiments are also included within the scope of the present invention: a method for manufacturing a current collector according to claim 1 having the features of claim 2; a method for manufacturing a current collector according to claim 2 having the features of claim 3; a method for manufacturing a current collector according to claim 1 having the features of claim 4; a method for manufacturing a current collector according to any one of claims 1 to 4 having the features of claim 5; a method for manufacturing a current collector according to any one of claims 1 to 5 having the features of claim 6; and a method for manufacturing a current collector according to any one of claims 1 to 6 having the features of claim 7. [Explanation of symbols]

[0060] 11a negative electrode current collector (first current collector), 11b Positive electrode current collector (second current collector).

Claims

1. A current collector comprising a metal or alloy powder and an electroless plating layer covering the metal or alloy powder, wherein the conductivity of the metal or alloy powder and the plating layer is approximately the same, or the conductivity of the metal or alloy powder is greater than the conductivity of the plating layer.

2. The metal powder is spread out, 2. The method for producing a current collector according to claim 1, wherein the current collector is formed by applying an autocatalytic electroless plating solution of the same kind as the metal powder, drying the solution, and solidifying the metal powder by plating.

3. 3. The method for producing a current collector according to claim 2, wherein the electroless plating solution is applied by an ink-jet method.

4. The metal powder; 2. The method for producing a current collector according to claim 1, wherein the metal powder is mixed with an autocatalytic electroless plating solution of the same type to form a slurry, which is then coated, dried, and solidified to form the current collector.

5. The method for producing a current collector according to any one of claims 1 to 4, wherein the metal or alloy powder is subjected to roll pressing.

6. The method for producing a current collector according to any one of claims 1 to 5, wherein an electroless plating solution is applied to the copper-based metal or alloy powder.

7. The method for producing a current collector according to any one of claims 1 to 5, wherein an electroless plating solution is applied to the nickel-based metal or alloy powder.

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