Current collector

Abstract

To provide a current collector that can form a battery with high energy density. [Solution] A current collector for a bipolar battery, wherein the current collector has a metal layer composed of Cu or Ni and a conductive resin layer containing metal particles as a conductive filler arranged in this order on a first surface of an Al foil, or the current collector has the conductive resin layer and the metal layer arranged in this order on the first surface of the Al foil, the metal layer being a vapor-deposited layer or a sputtered layer, and the thickness of the metal layer being 2 μm or less.

Description

[Technical Field]

[0001] The present disclosure relates to a current collector. [Background Art]

[0002] Various techniques have been proposed for batteries as disclosed in Patent Documents 1 and 2. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2022-081129 [Patent Document 2] Japanese Unexamined Patent Publication No. 2024-142426 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Patent Document 1 discloses a current collector including a first conductive resin layer containing a first conductive filler, and a second conductive resin layer formed on the first conductive resin layer and containing a second conductive filler, wherein the first conductive filler is conductive carbon, the second conductive filler contains at least one metal selected from the group consisting of platinum, gold, silver, copper, SUS (Stainless Used Steel), nickel and titanium, and the thickness of the first conductive resin layer is 50% or more of the thickness of the current collector. Patent Document 1 leaves room for improvement in terms of reducing the risk when pinholes occur. When a carbon-based filler is used, Li is conducted through the carbon, which makes it difficult to use the filler for a current collector for bipolar batteries. In addition, the increase in total thickness reduces the energy density of the resulting battery.

[0005] The present disclosure has been made in view of the above circumstances, and a main object of the present disclosure is to provide a current collector capable of forming a battery with high energy density. [Means for Solving the Problem]

[0006] In other words, this disclosure includes the following aspects: <1> A current collector for a bipolar battery, The current collector has a metal layer composed of Cu or Ni and a conductive resin layer containing metal particles as a conductive filler arranged in this order on the first surface of the Al foil, or The current collector is configured such that the conductive resin layer and the metal layer are arranged in this order on the first surface of the Al foil. The aforementioned metal layer is a vapor-deposited layer or a sputtered layer. A current collector in which the thickness of the aforementioned metal layer is 2 μm or less. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a current collector that can form a battery with high energy density. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing an example of a current collector according to the present disclosure. [Figure 2] Figure 2 is a schematic diagram showing another example of the current collector of this disclosure. [Modes for carrying out the invention]

[0009] Embodiments of the present disclosure are described below. Matters other than those specifically mentioned herein but necessary for the implementation of the present disclosure (e.g., general configuration and manufacturing process of current collectors not characterizing the present disclosure) can be understood as design matters for those skilled in the art based on prior art. The present disclosure can be implemented based on the content disclosed herein and common technical knowledge in the art. Furthermore, the dimensions (length, width, thickness, etc.) shown in the diagram do not necessarily reflect the actual dimensions.

[0010] In this disclosure, a current collector for a bipolar battery, The current collector has a metal layer composed of Cu or Ni and a conductive resin layer containing metal particles as a conductive filler arranged in this order on the first surface of the Al foil, or The current collector is configured such that the conductive resin layer and the metal layer are arranged in this order on the first surface of the Al foil. The aforementioned metal layer is a vapor-deposited layer or a sputtered layer. The present invention provides a current collector in which the thickness of the metal layer is 2 μm or less.

[0011] According to this disclosure, because carbon fillers are not used, the film capable of blocking the electrolyte has a two-layer structure (conductive resin layer and metal layer), resulting in an extremely low risk of pinhole formation. The metal layer is extremely thin, allowing for the formation of a battery with high energy density. Furthermore, it exhibits extremely high conductivity.

[0012] The current collector of this disclosure is for use in bipolar batteries. A bipolar battery includes a bipolar battery element. The bipolar battery element comprises an electrode (positive or negative electrode) having a current collector and an electrode layer (positive or negative electrode layer) disposed on at least one surface of the current collector. The bipolar battery element may also comprise a bipolar electrode having a current collector, a positive electrode layer disposed on one surface of the current collector, and a negative electrode layer disposed on the other surface of the current collector in the thickness direction. A bipolar battery may have bipolar electrodes, a positive electrode end electrode CA, and a negative electrode end electrode AN. The positive electrode end electrode CA has a current collector and a positive electrode layer disposed on one surface of the current collector. The negative electrode end electrode AN has a current collector and a negative electrode layer disposed on one surface of the current collector. A bipolar battery typically comprises a power generation unit U. The power generation unit U includes a positive electrode layer, a negative electrode layer, and a separator (electrolyte layer) positioned between the positive and negative electrode layers. A bipolar battery may have one power generation unit, or it may have two or more units. The positive electrode comprises a positive electrode layer and a positive electrode current collector. The positive electrode layer is a layer containing at least a positive electrode active material. Further, the positive electrode layer may optionally contain at least one of a solid electrolyte, a conductive material and a binder. The negative electrode includes a negative electrode layer and a negative electrode current collector. The negative electrode layer is a layer containing at least a negative electrode active material. Further, the negative electrode layer may optionally contain at least one of a solid electrolyte, a conductive material and a binder. The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least an electrolyte. The electrolyte may be a solid electrolyte or may be a liquid electrolyte (electrolytic solution).

[0013] The type of the battery in the present disclosure is not particularly limited, but is typically a lithium ion battery. Further, the battery in the present disclosure may be a liquid battery in which the electrolyte layer contains an electrolytic solution, or may be a solid battery in which the electrolyte layer contains a solid electrolyte. The solid battery may be a semi-solid battery or may be an all-solid-state battery. In the present disclosure, a semi-solid battery is a battery in which the electrolyte layer includes a solid component such as an inorganic solid electrolyte and a liquid component (for example, a solvent, an electrolytic solution, and the like). In the present disclosure, an all-solid-state battery is a battery in which the electrolyte layer includes only a solid component such as an inorganic solid electrolyte. Further, the battery in the present disclosure may be a primary battery or may be a secondary battery, and in particular, may be a secondary battery. This is because it can be repeatedly charged and discharged, and is useful, for example, as a vehicle-mounted battery.

[0014] Examples of uses of the battery include power supplies for vehicles such as hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), battery electric vehicles (BEV), gasoline vehicles, and diesel vehicles. In particular, the battery may be used as a driving power source for a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV) or a battery electric vehicle (BEV). Further, the battery may be used as a power source for moving bodies other than vehicles (for example, railways, ships, aircraft), or may be used as a power source for electrical products such as information processing apparatuses.

[0015] The current collector includes an Al foil, a metal layer, and a conductive resin layer. The current collector may have a metal layer and a conductive resin layer arranged in that order on the first surface of the Al foil. The current collector may have a conductive resin layer and a metal layer arranged in that order on the first surface of the Al foil.

[0016] Figure 1 is a schematic diagram showing an example of a current collector according to the present disclosure. As shown in Figure 1, the current collector 100 of this disclosure has a metal layer 12 and a conductive resin layer 13 arranged in this order on the first surface of the Al foil 11.

[0017] Figure 2 is a schematic diagram showing another example of the current collector of this disclosure. As shown in Figure 2, the current collector 200 of this disclosure has a conductive resin layer 13 and a metal layer 12 arranged in this order on the first surface of the Al foil 11.

[0018] The thickness of the aluminum foil may be 10 μm to 40 μm.

[0019] The conductive resin layer comprises a resin and metal particles as conductive fillers. The thickness of the conductive resin layer may be 2 μm to 10 μm. The resin may be a thermoplastic resin. Examples of thermoplastic resins include polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyimide resin (PI), liquid crystal polymer (LCP), and fluororesin. Examples of metal particles used as conductive fillers include Ni particles and Cu particles.

[0020] The metal layer is composed of Cu or Ni. The metal layer may also contain platinum, gold, silver, SUS, titanium, etc. The metal layer may consist of two layers: a Cu layer and a Ni layer. The metal layer may also consist of multiple layers, a combination of a layer composed of Cu or Ni and a layer composed of platinum, gold, silver, SUS, or titanium. The metal layer is either a vapor-deposited layer or a sputtered layer. The metal layer may be formed by vapor deposition, sputtering, wet plating (electrolytic / electroless), etc. The thickness of the metal layer may be 2 μm or less, 10 nm or more, 20 nm or more, 30 nm or more, 1 μm or less, or 50 nm or less. If the metal layer is thinner than 10 nm, it may not be able to adequately block the electrolyte. If the metal layer is thicker than 2 μm, the energy density of the battery decreases, and the cost increases further. [Examples]

[0021] (Example 1) (1) Compound preparation A compound was obtained by kneading a resin (adhesive PP) and a conductive filler (Ni powder) in a twin-screw extruder at 240°C in a predetermined proportion. • Resin: Adhesive PP (QE840 extrusion laminating type, manufactured by Mitsui Chemicals) • Conductive filler: Ni powder Composition ratio: Resin / Ni powder = 90 / 10 (mass%) (2) Preparation of the conductive resin layer The above compound was heated to 280°C in an extrusion laminating apparatus and directly laminated onto an Al foil (40 μm) to produce a laminated foil of conductive resin layer / Al foil. (3) Preparation of the current collector A current collector consisting of an Al foil (40 μm), a conductive resin layer (3 μm), and a Cu layer (10 μm) was fabricated by vapor deposition on a conductive resin layer.

[0022] (Example 2) A copper layer was formed on an aluminum foil by vapor deposition, and the compound was heated to 280°C in an extrusion laminating apparatus and directly laminated onto the copper layer to produce a current collector consisting of an aluminum foil (40 μm), a copper layer (10 μm), and a conductive resin layer (3 μm).

[0023] (Comparative Example 1) The above compound was heated to 280°C in an extrusion laminating apparatus and directly laminated onto an aluminum foil (40 μm) to produce a current collector consisting of an aluminum foil (40 μm) and a conductive resin layer (3 μm).

[0024] (Comparative Example 2) A copper layer was formed on an aluminum foil by vapor deposition, and a current collector consisting of an aluminum foil (40 μm) and a copper layer (10 μm) was fabricated.

[0025] (Comparative Example 3) The above compound was heated to 280°C in an extrusion laminating apparatus, directly laminated onto a substrate, and then peeled off the substrate to produce a current collector consisting of a single layer of conductive resin (3 μm).

[0026] [Prepare the batteries] A battery was fabricated using the current collectors from Examples 1-2 and Comparative Examples 1-3. <Positive electrode> In Examples 1-2 and Comparative Examples 1-2, the positive electrode layer was formed on the Al foil side, and in Comparative Example 3, the positive electrode layer was formed on one side of the conductive resin layer using the following materials. • Positive electrode active material: NCM (Lithium nickel-cobalt manganese oxide, manufactured by Sumitomo Metal Mining Co., Ltd.) • Conductive material: Acetylene black (Li435, manufactured by Denka) • Binder: PVdF (#7305, manufactured by Kureha Battery Materials Japan) NMP-based 5% solution Composition ratio: positive electrode active material / conductive material / binder = 95 / 2.5 / 2.5 (mass%) • Positive electrode layer, one side basis weight: 38 mg / cm² 2 ·Positive electrode layer density: 3.0g / cm 3 <Negative electrode> In Examples 1-2 and Comparative Examples 1-2, the negative electrode layer was formed on either the conductive resin layer side or the Cu layer side, while in Comparative Example 3, the negative electrode layer was formed on the other side of the conductive resin layer using the following materials. • Negative electrode active material: Amorphous coated graphite (manufactured by Hitachi Chemical Co., Ltd.) • Thickening agent: CMC (MAC800LD, manufactured by Nippon Paper Industries) • Binder: SBR (AL-2001, manufactured by A&L Japan) • Composition ratio: Negative electrode active material / thickener / binder = 97 / 0.7 / 2.3 (mass%) • Negative electrode layer, one side: 22.6 mg / cm² 2 ·Negative electrode layer density: 1.2gm / cm 3

[0027] [Pinhole frequency evaluation] For the current collectors of Examples 1-2 and Comparative Examples 1-3, a wide area was observed using a microscope, and the number of defects was counted. For the current collectors in Examples 1 and 2, the number of pinholes was 0.03 per meter. 2 Therefore, the number of pinholes is small, and the positions of the pinholes in the two layers, the vapor-deposited layer and the conductive resin layer, hardly overlap, resulting in significantly higher pinhole resistance. For the current collector in Comparative Example 1, the number of pinholes was 2.2 per meter. 2 Therefore, it has a large number of pinholes and lacks a vapor-deposited layer, resulting in low pinhole resistance. For the current collector in Comparative Example 2, the number of pinholes was 11,000 / m 2 Therefore, it has a large number of pinholes in the vapor-deposited layer and lacks a conductive resin layer, resulting in low pinhole resistance. For the current collector in Comparative Example 3, the number of pinholes was 0.4 per meter. 2 Therefore, although the number of pinholes in the conductive resin layer is small, the pinhole resistance is low because there is only one conductive resin layer.

[0028] [Battery performance and structural strength evaluation] When the battery performance and structural strength of batteries fabricated using the current collectors of Examples 1-2 and Comparative Examples 1-3 were evaluated by a predetermined method, Examples 1-2 and Comparative Examples 1-2 all showed good battery performance and structural strength. Comparative Example 3 showed good battery performance, but its structural strength was low due to the lack of thick Al foil.

[0029] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Explanation of symbols]

[0030] 11 ...Al foil 12...metal layer 13 ... Conductive resin layer 100 ... Current collector 200 ... Current collector

Claims

[Claim 1] A current collector for a bipolar battery, The current collector has a metal layer composed of Cu or Ni and a conductive resin layer containing metal particles as a conductive filler arranged in this order on the first surface of the Al foil, or The current collector is configured such that the conductive resin layer and the metal layer are arranged in this order on the first surface of the Al foil. The aforementioned metal layer is a vapor-deposited layer or a sputtered layer. A current collector in which the thickness of the aforementioned metal layer is 2 μm or less.

Images