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KR-20260067506-A - POSITIVE ELECTRODE FOR RECHARGEABLE LITHIUM BATTERIES AND RECHARGEABLE LITHIUM BATTERIES INCLUDING THE SAME

KR20260067506AKR 20260067506 AKR20260067506 AKR 20260067506AKR-20260067506-A

Abstract

The present invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery including the same, wherein the positive electrode for the lithium secondary battery comprises: a positive electrode current collector; a first positive electrode active material layer located on the positive electrode current collector and containing a first positive electrode active material comprising a lithium iron phosphate-based compound; and a second positive electrode active material layer located on the first positive electrode active material layer and containing a second positive electrode active material comprising a lithium nickel-based composite oxide and a lithium manganese-based oxide.

Inventors

  • 두성욱

Assignees

  • 삼성에스디아이 주식회사

Dates

Publication Date
20260513
Application Date
20241105

Claims (20)

  1. Positive current collector; A first positive active material layer located on the positive current collector and containing a first positive active material comprising a lithium iron phosphate-based compound; and A second positive active material layer located on the first positive active material layer and containing a second positive active material comprising a lithium nickel-based composite oxide and a third positive active material comprising a lithium manganese-based oxide; comprising Cathode for lithium secondary batteries.
  2. In Paragraph 1, The above lithium iron phosphate-based compound is represented by the following chemical formula 1 or chemical formula 2, Cathode for lithium secondary batteries: [Chemical Formula 1] Li a1 Fe (1-x1) M 1 x1 PO 4 In Chemical Formula 1, 0.9≤a1≤1.5, 0≤x1≤0.4, and M1 is Al, Ca, Ce, Cr, Cu, La, Mg, Mn, Mo, Nb, Ni, Sn, Sr, Ti, V, W, Y, Zn, Zr, or a combination thereof, and [Chemical Formula 2] Li a2 Mn x2 Fe (1-x2-y2) M 2 y2 PO 4 In Chemical Formula 2, 0.9≤a2≤1.5, 0.1≤x2≤0.9, 0≤y2<0.9, M2 is Al, Ca, Ce, Cr, Cu, La, Mg, Mo, Nb, Ni, Sn, Sr, Ti, V, W, Y, Zn, Zr, or a combination thereof.
  3. In paragraph 1, The first positive active material is in the form of particles, and is in the form of first particles, second particles, or a mixture thereof. The first particle above is a secondary particle formed by the aggregation of a plurality of primary particles, and The above second particle is in the form of a single particle, Cathode for lithium secondary batteries.
  4. In paragraph 3, The average particle size (D 50 ) of the secondary particles of the first particle is 5 μm to 20 μm, and the average particle size (D 50 ) of the primary particles forming the secondary particles is 0.1 μm to 2 μm. The average particle size (D 50 ) of the single particles of the second particle is 0.5 μm to 5 μm, Cathode for lithium secondary batteries.
  5. In paragraph 3, With respect to 100 weight% of the first positive active material, the content of the first particle is 20 weight% to 100 weight%, and the content of the second particle is 0 weight% to 80 weight%. Cathode for lithium secondary batteries.
  6. In paragraph 3, The first positive active material is A first particle further comprising a carbon coating layer located on the surface of the secondary particle, and/or A second particle comprising a carbon coating layer located on the surface of the above single particle, Cathode for lithium secondary batteries.
  7. In paragraph 6, The carbon coating layer is included in an amount of 0.1% to 3.9% by weight relative to 100% by weight of the first particle, and The carbon coating layer is included in an amount of 0.1% to 3.9% by weight with respect to 100% by weight of the second particle. Cathode for lithium secondary batteries.
  8. In Paragraph 1, The lithium nickel-based composite oxide of the second positive electrode active material is represented by the following chemical formula 3, Cathode for lithium secondary batteries: [Chemical Formula 3] Li a3 Ni x3 M 3 y3 M 4 z3 O 2- b3 In the above chemical formula 3, 0.9≤a3≤1.2, 0.3≤x3<1, 0<y3≤0.7, 0≤z3≤0.7, 0.9≤x3+y3+z3≤1.1, and 0≤b3≤0.1, M3 and M4 are each independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.
  9. In Paragraph 1, The lithium nickel-based composite oxide of the second positive electrode active material is a positive electrode for a lithium secondary battery containing 80 mol% or more of nickel with respect to 100 mol% of the total metal excluding lithium.
  10. In Paragraph 1, The second positive electrode active material comprises large particles having an average particle size (D 50 ) of 9 μm to 20 μm, small particles having an average particle size (D 50 ) of 1 μm to 8 μm, or a combination thereof. Cathode for lithium secondary batteries.
  11. In Paragraph 10, The above second positive active material includes both the above alleles and the above subatomic particles, and The above alleles and the above subatomic particles are mixed in a weight ratio of 20:80 to 95:5,
  12. In paragraph 1, The above lithium manganese-based oxide is represented by the following chemical formula 6, Cathode for lithium secondary batteries: [Chemical Formula 6] Li a6 Mn x6 M 8 y6 O 4- b6 In chemical formula 6, 0.9≤a6≤1.8, 1.7≤x6≤2, 0≤y6≤0.3, 1.9≤x6+y6≤2.1, and 0≤b6≤0.1, M8 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y and Zr, and X is one or more elements selected from F, P and S. Cathode for lithium secondary batteries.
  13. In Paragraph 1, The third positive electrode active material is in the form of secondary particles formed by the aggregation of multiple primary particles, in the form of single particles, or in a mixed form thereof, and The average particle size (D 50 ) of the above secondary particles is 5 μm to 15 μm, and The average particle size (D 50 ) of the above single particles is 0.1 μm to 10 μm, Cathode for lithium secondary batteries.
  14. In paragraph 1, The weight ratio of the second positive active material and the third positive active material in the second positive active material layer is 10:90 to 90:10, Cathode for lithium secondary batteries.
  15. In paragraph 1, In the entire first positive active material layer and the second positive active material layer, with respect to a total of 100 weight% of the first positive active material, the second positive active material, and the third positive active material, the first positive active material is included in an amount of 10 weight% to 70 weight%, the second positive active material is included in an amount of 5 weight% to 50 weight%, and the third positive active material is included in an amount of 20 weight% to 80 weight%. Cathode for lithium secondary batteries.
  16. In paragraph 1, A cathode for a lithium secondary battery, wherein the manganese content relative to 100 mol% of the total metal excluding lithium in the entire first cathode active material layer and the second cathode active material layer is 30 mol% to 70 mol%.
  17. In paragraph 1, The first positive active material layer further comprises a first binder, a first conductive material, or a combination thereof, and The second positive active material layer further comprises a second binder, a second conductive material, or a combination thereof. Cathode for lithium secondary batteries.
  18. In paragraph 1, The loading level of the first positive active material layer is 5 mg/ cm² to 25 mg/ cm² , and The loading level of the second positive active material layer is 5 mg/ cm² to 25 mg/ cm² , Cathode for lithium secondary batteries.
  19. In paragraph 1, The total composite density of the first positive active material layer and the second positive active material layer is 2.0 g/cc to 4.0 g/cc, Cathode for lithium secondary batteries.
  20. A lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte according to any one of claims 1 to 19.

Description

Positive electrode for rechargeable lithium batteries and rechargeable lithium batteries including the same This invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery containing the same. Lithium-ion batteries are widely used as power sources for mobile information terminals such as smartphones and laptops because they offer high energy density and portability. Recently, active research is being conducted on lithium-ion batteries with high safety and high capacity for use as power sources for hybrid or electric vehicles, or for power storage. Recently, there has been a demand for lithium secondary batteries capable of securing rapid charging characteristics while ensuring high safety, leading to the proposal of low-cost lithium iron phosphate-based compounds as cathode active materials. However, lithium iron phosphate-based compounds have limitations in realizing high energy density and high capacity. Attempts have been made to form electrode plates by mixing lithium nickel-based composite oxides and lithium iron phosphate-based compounds to secure high energy density, high stability, and high capacity while simultaneously enhancing price competitiveness. However, when manufacturing electrode plates by mixing lithium nickel-based composite oxides and lithium iron phosphate-based compounds, there is a problem of voltage divergence, which leads to reduced capacity and degraded battery life characteristics due to the degradation of the cathode active material. FIGS. 1 to 4 are schematic drawings illustrating a lithium secondary battery according to one embodiment. Figure 5 is a graph showing the voltage profile according to the capacity at the initial charge and discharge for the lithium secondary battery of Comparative Example 4 and the lithium secondary battery of Comparative Example 5. FIG. 6 is a schematic diagram showing an anode according to one embodiment. Specific embodiments are described below in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. The terms used herein are for describing exemplary embodiments only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. Here, "combinations of these" refers to mixtures of components, laminates, composites, copolymers, alloys, blends, reaction products, etc. The terms "include," "equip," or "have" used herein 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 drawings, thicknesses have been enlarged to clearly represent various layers and regions, and the same reference numerals have been used for similar parts throughout the specification. When a part such as a layer, film, region, or plate is described as being "on" or "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between. Conversely, when a part is described as being "immediately on" another part, it means that there is no other part in between. In addition, the term “layer” here includes not only the shape formed on the entire surface when viewed in a plan view, but also the shape formed on some surfaces. The average particle size can be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by using transmission electron microscope images or scanning electron microscope images. Alternatively, the average particle size value can be obtained by measuring using dynamic light scattering and performing data analysis to count the number of particles for each particle size range, and then calculating from this. Unless otherwise defined, the average particle size may refer to the diameter (D 50 ) of a particle whose cumulative volume is 50% of the particle size distribution. Additionally, unless otherwise defined, the average particle size may be obtained by randomly measuring the size (diameter or length of the major axis) of about 20 particles from a scanning electron microscope image to obtain a particle size distribution, and taking the diameter (D 50 ) of the particle whose cumulative volume is 50% of the particle size distribution as the average particle size. Here, “or” is not interpreted in an exclusive sense; for example, “A or B” is interpreted to include A, B, A+B, etc. The term “metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semimetals). anode In one embodiment, a positive electrode for a lithium secondary battery is provided, comprising: a positive electrode current collect