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KR-20260064634-A - POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY

KR20260064634AKR 20260064634 AKR20260064634 AKR 20260064634AKR-20260064634-A

Abstract

The present invention relates to a positive electrode comprising: a positive electrode current collector; a positive electrode active material layer comprising a first positive electrode active material layer located on the positive electrode current collector and a second positive electrode active material layer located on the first positive electrode active material layer; wherein the positive electrode active material layer comprises a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material layer comprises the first positive electrode active material and the second positive electrode active material in a weight ratio of 7:3 to 6:4, and the second positive electrode active material layer comprises the first positive electrode active material and the second positive electrode active material in a weight ratio of 3:7 to 4:6, wherein the first positive electrode active material has a larger average particle size (D 50 ) than the second positive electrode active material, and the second positive electrode active material comprises a single particle.

Inventors

  • 박은희

Assignees

  • 주식회사 엘지에너지솔루션

Dates

Publication Date
20260507
Application Date
20251030
Priority Date
20241031

Claims (12)

  1. A positive current collector; a positive active material layer comprising a first positive active material layer located on the positive current collector and a second positive active material layer located on the first positive active material layer; and The above positive active material layer includes a first positive active material and a second positive active material, and The first positive active material layer comprises the first positive active material and the second positive active material in a weight ratio of 7:3 to 6:4, and The second positive active material layer comprises the first positive active material and the second positive active material in a weight ratio of 3:7 to 4:6, and The first positive active material has a larger average particle size (D 50 ) than the second positive active material, The above second positive active material is a positive electrode comprising single-particle type particles.
  2. In paragraph 1, The above-mentioned first positive electrode active material comprises a lithium nickel-based oxide containing 80 mol% or more of nickel among the total metals excluding lithium, forming a positive electrode.
  3. In paragraph 1, The above second positive electrode active material comprises a lithium nickel-based oxide containing 80 mol% or more of nickel among the total metals excluding lithium, and is a positive electrode.
  4. In paragraph 1, The first positive active material and the second positive active material are positives having an average particle size (D 50 ) ratio of 1.3:1 to 4:1.
  5. In paragraph 1, The first positive active material is a positive electrode having an average particle size (D 50 ) of 8 to 14 μm.
  6. In paragraph 1, The above second positive active material is a positive electrode having an average particle size (D 50 ) of 2 to 6 μm.
  7. In paragraph 1, The above-mentioned first positive active material is a positive electrode comprising secondary particles.
  8. In paragraph 1, The positive electrode active material layer comprises the first positive electrode active material and the second positive electrode active material in a weight ratio of 4:6 to 6:4.
  9. In paragraph 1, The anode, wherein the porosity of the first anode active material layer is higher than the porosity of the second anode active material layer.
  10. In paragraph 1, An anode, wherein the ratio of the total weight of the first positive active material and the second positive active material included in the first positive active material layer to the total weight of the first positive active material and the second positive active material included in the second positive active material layer is 4:6 to 6:4.
  11. A lithium secondary battery comprising: a positive electrode according to any one of claims 1 to 10; a negative electrode opposite to the positive electrode; and an electrolyte.
  12. In Paragraph 11, A lithium secondary battery in which the above-mentioned negative electrode comprises a negative electrode active material including a carbon-based negative electrode active material.

Description

Positive Electrode and Lithium Secondary Battery The present invention relates to a positive electrode and a lithium secondary battery, and more specifically, to a positive electrode and a lithium secondary battery capable of reducing particle breakage while improving energy density. With the technological advancement of electric vehicles and portable electronic devices, the demand for lithium-ion batteries as an energy source is rapidly increasing. In particular, due to recent advancements in electric vehicle technology, there is a demand for batteries with high energy density. As one of the technologies to increase the energy density of lithium secondary batteries, a technology has been developed to apply a cathode material having a bimodal structure in which a cathode active material having a large particle size is mixed with a cathode active material having a small particle size. Specifically, in a lithium secondary battery applying a cathode material having a bimodal structure, the energy density of the cathode can be improved because the small-particle cathode active material can fill the voids between the large-particle cathode active material particles. In addition, by rolling an anode containing such a bimodal structured anode material, an anode with a denser structure can be manufactured, thereby further improving the energy density of the anode. However, during the rolling process, breakage of the anode active material particles may occur, and such particle breakage can lead to problems such as degradation of the anode active material. Therefore, a technology has recently been developed to further increase rolling density while reducing particle breakage of the small-particle cathode active material by applying single-particle type particles with excellent particle strength as the small-particle cathode active material included in the bimodal structured cathode material. Meanwhile, when secondary particles are applied as conventional small-particle cathode active materials, the small-particle cathode active material has relatively weaker particle strength than the large-particle cathode active material; thus, during the rolling process, the small-particle cathode active material particles break first and act as a buffer, preventing particle breakage of the large-particle cathode active material. However, as described above, when single-particle type particles are applied to the small-particle cathode active material, particle breakage of the large-particle cathode active material increases as the particle strength of the small-particle cathode active material increases. This can lead to problems such as deterioration of battery life and resistance characteristics, increased gas generation by the large-particle cathode active material, and reduced thermal stability. Therefore, there is a need to develop technology capable of solving these problems. The present invention will be described in more detail below. Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “having,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof. In the present invention, "single particle type" refers to a particle composed of 50 or fewer nodules, and is a concept that includes a single particle composed of one nodule and a pseudo-single particle which is a complex of 2 to 50 nodules. The above “nodule” is a sub-grain unit constituting a single particle and a pseudo-single particle, and may be a single crystal that does not have crystalline grain boundaries, or a polycrystalline one in which no grain boundaries appear to exist when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope. In the present invention, "secondary particle" refers to a particle formed by the aggregation of a plurality of primary particles, for example, tens to hundreds of primary particles. Specifically, the secondary particle may be an aggregate of more than 50 primary particles. In the present invention, the term “particle” is a concept that includes any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle. In this specifi