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CN-122000283-A - Positive electrode for rechargeable lithium battery and rechargeable lithium battery including the same

CN122000283ACN 122000283 ACN122000283 ACN 122000283ACN-122000283-A

Abstract

A positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are disclosed. The positive electrode for a rechargeable lithium battery includes a positive electrode current collector, a first positive electrode active material layer on the positive electrode current collector and including a first positive electrode active material including a lithium iron phosphate-based compound, and a second positive electrode active material layer on the first positive electrode active material layer and including a second positive electrode active material including a lithium nickel-based composite oxide and a third positive electrode active material including a lithium manganese-based oxide.

Inventors

  • Du Chengxu

Assignees

  • 三星SDI株式会社

Dates

Publication Date
20260508
Application Date
20251030
Priority Date
20241105

Claims (20)

  1. 1. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: A positive electrode current collector; A first positive electrode active material layer on the positive electrode current collector and including a first positive electrode active material containing a lithium iron phosphate compound, and A second positive electrode active material layer on the first positive electrode active material layer, and including a second positive electrode active material including a lithium nickel-based composite oxide and a third positive electrode active material including a lithium manganese-based oxide.
  2. 2. The positive electrode according to claim 1, wherein the lithium iron phosphate-based compound is represented by one of chemical formula 1 and chemical formula 2: Chemical formula 1: Li a1 Fe (1-x1) M 1 x1 PO 4 Wherein in chemical formula 1, 0.9≤a1≤1.5, 0≤x1≤0.4, and M 1 includes at least one of Al, ca, ce, cr, cu, la, mg, mn, mo, nb, ni, sn, sr, ti, V, W, Y, zn and Zr, Chemical formula 2: Li a2 Mn x2 Fe (1-x2-y2) M 2 y2 PO 4 Wherein, in chemical formula 2, 0.9≤a2≤ 1.5,0.1≤x2≤0.9, 0≤y2 <0.9, and M 2 includes at least one of Al, ca, ce, cr, cu, la, mg, mo, nb, ni, sn, sr, ti, V, W, Y, zn and Zr.
  3. 3. The positive electrode of claim 1, wherein: the first positive electrode active material includes one of first particles, second particles, and a mixture thereof, The first particles include secondary particles formed by aggregation of a plurality of primary particles, and The second particles are in the form of individual particles.
  4. 4. The positive electrode according to claim 3, wherein: The secondary particles of the first particles have an average particle diameter D 50 in the range of 5 μm to 20 μm, The primary particles forming the secondary particles have an average particle diameter D 50 in the range of 0.1 μm to 2 μm, and The average particle diameter D 50 of the individual particles of the second particles is in the range of 0.5 μm to 5 μm.
  5. 5. The positive electrode according to claim 3, wherein the amount of the first particles is in the range of 20 to 100wt% based on 100wt% of the first positive electrode active material, and The amount of the second particles is in the range of 0wt% to 80 wt%.
  6. 6. The positive electrode according to claim 3, wherein the first positive electrode active material further comprises at least one of: A carbon coating layer formed on the surface of the secondary particles of the first particles; a carbon coating layer formed on the surface of the primary particles forming the secondary particles of the first particles, and A carbon coating layer formed on the surface of the individual particles of the second particles.
  7. 7. The positive electrode of claim 6 wherein: Including the carbon coating in an amount ranging from 0.1wt% to 3.9wt% based on 100wt% of the first particles, and The carbon coating is included in an amount ranging from 0.1wt% to 3.9wt% based on 100wt% of the second particles.
  8. 8. The positive electrode according to claim 1, wherein the lithium-nickel-based composite oxide in the second positive electrode active material is represented by chemical formula 3: Chemical formula 3: Li a3 Ni x3 M 3 y3 M 4 z3 O 2-b3 X b3 Wherein 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 in chemical formula 3, M 3 and M 4 each independently include one or more of 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 includes one or more of F, P and S.
  9. 9. The positive electrode according to claim 1, wherein the lithium-nickel based composite oxide in the second positive electrode active material includes nickel in an amount of 80mol% or more based on 100mol% of total metals other than lithium.
  10. 10. The positive electrode according to claim 1, wherein the second positive electrode active material includes at least one of large particles having an average particle diameter D 50 in a range of 9 μm to 20 μm and small particles having an average particle diameter D 50 in a range of 1 μm to 8 μm.
  11. 11. The positive electrode of claim 10 wherein: The second positive electrode active material includes both the large particles and the small particles, and The large particles and the small particles are mixed in a weight ratio in the range of 20:80 to 95:5.
  12. 12. The positive electrode according to claim 1, wherein the lithium manganese-based oxide is represented by chemical formula 6: chemical formula 6: Li a6 Mn x6 M 8 y6 O 4-b6 X b6 Wherein 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, M 8 includes one or more of Al, B, ba, ca, ce, cr, cu, fe, mg, mo, nb, si, sn, sr, ti, V, W, Y, zn and Zr, and X includes one or more of F, P and S.
  13. 13. The positive electrode of claim 1, wherein: The third positive electrode active material includes secondary particles formed by aggregation of a plurality of primary particles, single particles or a mixture thereof, The secondary particles have an average particle diameter D 50 to 15 μm, and The individual particles have an average particle diameter D 50 in the range of 0.1 μm to 10 μm.
  14. 14. The positive electrode according to claim 1, wherein a weight ratio of the second positive electrode active material and the third positive electrode active material in the second positive electrode active material layer is in a range of 10:90 to 90:10.
  15. 15. The positive electrode of claim 1, wherein: In the total amount of the first positive electrode active material layer and the second positive electrode active material layer, the first positive electrode active material is included in an amount in the range of 10wt% to 70wt%, the second positive electrode active material is included in an amount in the range of 10wt% to 50wt%, and the third positive electrode active material is included in an amount in the range of 20wt% to 80wt%, based on 100wt% of the total amount of the first positive electrode active material, the second positive electrode active material, and the third positive electrode active material.
  16. 16. The positive electrode according to claim 1, wherein a manganese content in a total amount of the first positive electrode active material layer and the second positive electrode active material layer is in a range of 30mol% to 70mol%, based on 100mol% of total metals other than lithium.
  17. 17. The positive electrode of claim 1, wherein: the first positive electrode active material layer further includes at least one of a first binder and a first conductive material, and The second positive electrode active material layer further includes at least one of a second binder and a second conductive material.
  18. 18. The positive electrode of claim 1, wherein: The load level of the first positive electrode active material layer is in the range of 5mg/cm 2 to 25mg/cm 2 , and The load level of the second positive electrode active material layer is in the range of 5mg/cm 2 to 25mg/cm 2 .
  19. 19. The positive electrode according to claim 1, wherein a total mixture density of the first positive electrode active material layer and the second positive electrode active material layer is in a range of 2.0g/cc to 4.0 g/cc.
  20. 20. A rechargeable lithium battery, the rechargeable lithium battery comprising: the positive electrode according to any one of claims 1 to 19, A negative electrode, and An electrolyte.

Description

Positive electrode for rechargeable lithium battery and rechargeable lithium battery including the same Technical Field A positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are disclosed. Background Rechargeable lithium batteries, which are easy to carry and realize high energy density, are widely used as power sources for mobile information terminals such as smart phones, laptop computers, etc. It may be advantageous to obtain a rechargeable lithium battery having high safety and high capacity for use as a power source for hybrid vehicles and electric vehicles or for storing electric power. In addition, since rechargeable lithium batteries are generally required to achieve rapid charge characteristics as well as high safety, low-cost lithium iron phosphate-based compounds can constitute positive electrode active materials. However, lithium iron phosphate-based compounds have limitations in exhibiting 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 achieve high energy density, high stability and high capacity while also improving price competitiveness. However, when the electrode plate is manufactured by mixing the lithium nickel-based composite oxide and the lithium iron phosphate-based compound, separation of the operating voltage may occur, which reduces the capacity and deteriorates the cycle life characteristics of the battery due to deterioration of the positive electrode active material. Disclosure of Invention Some example embodiments include a positive electrode for a rechargeable lithium battery that improves rate performance and cycle life characteristics without separating an operating voltage by mixing three types of positive electrode active materials and adopting a double-layer structure, and a rechargeable lithium battery including the same. In some example embodiments, a positive electrode for a rechargeable lithium battery includes a positive electrode current collector, a first positive electrode active material layer on the positive electrode current collector and including a first positive electrode active material including a lithium iron phosphate-based compound, and a second positive electrode active material layer on the first positive electrode active material layer and including a second positive electrode active material including a lithium nickel-based composite oxide and a third positive electrode active material including a lithium manganese-based oxide. In some example embodiments, a rechargeable lithium battery includes the aforementioned positive electrode, negative electrode, and electrolyte. The positive electrode for a rechargeable lithium battery according to some example embodiments includes a low-cost lithium iron phosphate-based positive electrode active material that is structurally stable, a lithium nickel-based positive electrode active material that has high capacity and energy density, and a low-cost lithium manganese-based positive electrode active material that exhibits capacity at a voltage of about 4V, and adopts a double-layer structure so that the operating voltage is not separated, and can improve rate performance and cycle life characteristics. Drawings Fig. 1 to 4 are schematic views illustrating a rechargeable lithium battery according to some example embodiments. Fig. 5 is a graph showing voltage distribution according to capacity at the time of first charge and discharge of the rechargeable lithium battery cell of comparative example 4 and the rechargeable lithium battery cell of comparative example 5. Fig. 6 is a schematic diagram illustrating a positive electrode according to some example embodiments. Detailed Description Hereinafter, example embodiments are described in detail so that those skilled in the art can easily implement the example embodiments. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. The terminology used herein is for the purpose of describing example embodiments only and is not intended to be limiting of the disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions. As used herein, "combination thereof" means mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of the components. Here, it should be understood that terms such as "comprises," "comprising," or "having" are intended to indicate the presence of the features, amounts, steps, elements, or combinations thereof that are shown, but do not preclude the possibility of the presence or addition of one or more other features, amounts, steps, elements, or combinations thereof. In the drawings, the thickness of layers, films, plates, regions, etc. may be exaggerated for clarity, and like reference numer