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KR-20260062872-A - POSITIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY

KR20260062872AKR 20260062872 AKR20260062872 AKR 20260062872AKR-20260062872-A

Abstract

The present invention provides a positive electrode for a lithium-ion secondary battery having excellent adhesion to the current collector and suppressed cracking, and a lithium-ion secondary battery having excellent cycle characteristics. A positive electrode for a lithium-ion secondary battery comprising a current collector, a coating layer comprising a conductive material and a non-aqueous binder, and an active material layer, wherein the non-aqueous binder comprises a conjugated diene copolymer having specific requirements, the content of the conductive material is 40.0 parts by mass or more and 99.9 parts by mass or less per 100 parts by mass of the coating layer, and the content of the non-aqueous binder is 0.1 parts by mass or more and 60.0 parts by mass or less per 100 parts by mass of the coating layer.

Inventors

  • 야스모토, 아츠시
  • 콘도, 토모히로

Assignees

  • 아사히 가세이 가부시키가이샤

Dates

Publication Date
20260507
Application Date
20251028
Priority Date
20241029

Claims (17)

  1. A positive electrode for a lithium-ion secondary battery comprising a current collector, a coating layer including a conductive material and a non-aqueous binder, and an active material layer, and The above-mentioned non-aqueous binder comprises a conjugated diene copolymer having the following requirements (a) to (d), and The content of the conductive material is 40.0 parts by mass or more and 99.9 parts by mass or less per 100 parts by mass of the coating layer, and The content of the above-mentioned non-aqueous binder is 0.1 parts by mass or more and 60.0 parts by mass or less per 100 parts by mass of the coating layer, Positive electrode for lithium-ion secondary batteries. Requirement (a): The content of aromatic vinyl monomer units is 6 mass% or more and 80 mass% or less with respect to the total amount of the conjugated diene copolymer. Requirement (b): The amount of 1,2-vinyl bonds to conjugated diene monomer units in the above conjugated diene copolymer is 10 mol% or more and 60 mol% or less. Requirement (c): The ratio of 1,4-cis bonds to 1,4-trans bonds in the above conjugated diene copolymer is 30:70 to 50:50. Requirement (d): Weight-average molecular weight is 100,000 or more and 2,000,000 or less.
  2. In claim 1, the Mooney viscosity of the conjugated diene copolymer under measurement conditions at 100°C is 30 or more and 200 or less, Positive electrode for lithium-ion secondary batteries.
  3. In claim 1, the content of the aromatic vinyl monomer unit is 30 mass% or more and 70 mass% or less with respect to the total amount of the conjugated diene copolymer, Positive electrode for lithium-ion secondary batteries.
  4. In claim 1, the content of the aromatic vinyl monomer block is 5.0 mass% or more and 40.0 mass% or less with respect to the total amount of the conjugated diene copolymer, Positive electrode for lithium-ion secondary batteries.
  5. In claim 1, the blocking rate of the aromatic vinyl monomer block in the conjugated diene copolymer is 15.0% or more and 85.0% or less, Positive electrode for lithium-ion secondary batteries.
  6. In claim 1, the respective contents of zinc, aluminum, copper, and iron are 50 ppm or less with respect to the total amount of the conjugated diene copolymer, Positive electrode for lithium-ion secondary batteries.
  7. In claim 1, the total content of zinc, aluminum, copper, and iron is 50 ppm or less with respect to the total amount of the conjugated diene copolymer, Positive electrode for lithium-ion secondary batteries.
  8. In claim 1, the total hydrogenation rate of the conjugated diene copolymer is 10% to 99%, Positive electrode for lithium-ion secondary batteries.
  9. In claim 1, the 1,2-hydrogen addition rate of the conjugated diene copolymer is 80% or more, Positive electrode for lithium-ion secondary batteries.
  10. In claim 1, the thickness of the coating layer is 0.1㎛ or more and 10㎛ or less, Positive electrode for lithium-ion secondary batteries.
  11. In claim 1, the conductive material comprises at least one selected from the group consisting of carbon black, graphite, carbon nanotubes, and aluminum hydroxide, Positive electrode for lithium-ion secondary batteries.
  12. In claim 1, the coating layer does not include a positive electrode active material, Positive electrode for lithium-ion secondary batteries.
  13. In paragraph 1, the current collector comprises aluminum, Positive electrode for lithium-ion secondary batteries.
  14. In claim 1, the active material layer comprises a binder, The above binder comprises polyvinylidene fluoride, Positive electrode for lithium-ion secondary batteries.
  15. In claim 1, the active material layer comprises an active material, The above active material comprises at least one selected from the group consisting of lithium iron phosphate, lithium magnesium iron phosphate, and lithium iron oxide, Positive electrode for lithium-ion secondary batteries.
  16. A positive electrode for a lithium-ion secondary battery as described in claim 1, Lithium-ion secondary battery.
  17. In Clause 16, additionally, including an electrolyte, Lithium-ion secondary battery.

Description

Positive electrode for lithium-ion secondary battery and lithium-ion secondary battery The present invention relates to a positive electrode for a lithium-ion secondary battery and a lithium-ion secondary battery. Conventionally, as a method for manufacturing electrodes used in electrochemical devices such as lithium-ion secondary batteries, a liquid composition in which a binder or a thickener is added to an electrode active material is applied to the surface of a current collector and dried to form an electrode layer on said current collector. Here, polyvinylidene fluoride (PVDF) is known as a binder capable of forming an electrode layer that has high adhesion to the metal constituting the current collector on the positive electrode side and also has high flexibility. In addition, conventional lithium secondary batteries include a positive electrode, a negative electrode, a separator, and an electrolyte, and as the positive electrode, an active material layer is formed on a current collector. Here, in order to increase the adhesion or conductivity between the positive electrode current collector and the active material layer, a conductive material such as carbon black is coated on the current collector. At this time, materials that play the role of holding the conductive material such as carbon black on the current collector include, for example, styrene-butadiene latex or polyvinylidene fluoride. For example, Patent Document 1 discloses a positive electrode for a lithium-ion secondary battery using styrene-butadiene latex as a binder for a carbon coating. Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "present embodiments") will be described in detail. Furthermore, the present embodiments described below are examples for explaining the present invention, and the present invention is not limited to the forms shown below. The present invention may be implemented with various modifications within the scope of its gist. Positive electrode for lithium-ion secondary batteries The positive electrode for a lithium-ion secondary battery according to the present embodiment comprises a current collector, a coating layer comprising a conductive material and a non-aqueous binder, and an active material layer comprising an active material and a binder, wherein the non-aqueous binder comprises a conjugated diene copolymer having the following requirements (a) to (d), the content of the conductive material is 40.0 parts by mass or more and 99.9 parts by mass or less per 100 parts by mass of the coating layer, and the content of the non-aqueous binder is 0.1 parts by mass or more and 60.0 parts by mass or less per 100 parts by mass of the coating layer. Requirement (a): The content of aromatic vinyl monomer units is 6 mass% or more and 80 mass% or less with respect to the total amount of conjugated diene copolymer. Requirement (b): The amount of 1,2-vinyl bonds to conjugated diene monomer units in the conjugated diene copolymer is 10 mol% or more and 60 mol% or less. Requirement (c): The ratio of 1,4-cis bonds to 1,4-trans bonds in the conjugated diene copolymer is 30:70 to 50:50. Requirement (d): Weight-average molecular weight is 100,000 or more and 2,000,000 or less. [Whole House] As a current collector used for the positive electrode of a lithium-ion secondary battery according to the present embodiment, a material having high conductivity that does not cause chemical changes in the battery may be used. As a material for the current collector, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used, and in the case of aluminum or stainless steel, a material surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the current collector may be in the form of a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc. Furthermore, the adhesion to the active material may be increased by expanding the surface area by having fine irregularities on the surface. In addition, the average thickness of the current collector can be appropriately applied to be 3 to 500 μm, taking into consideration the conductivity of the manufactured positive electrode and the total thickness. As for the material for the entire house, it is desirable to include aluminum in terms of price, weight, and supply stability. [Coating layer] The coating layer of the present embodiment comprises at least a conductive material and a non-aqueous binder. The coating layer may additionally include other components. As other components, it may include an active material for the positive electrode, but from the perspective of improving the freedom of selection of the active material layer, it is preferable not to include an active material for the positive electrode in the coating layer. In addition, from the perspective of conductivity, it may include carboxymethylcellulose as a thickener, but from the perspective of improving conductivity by i