Search

US-20260128287-A1 - POSITIVE ELECTRODE FOR RECHARGEABLE LITHIUM BATTERIES AND RECHARGEABLE LITHIUM BATTERIES INCLUDING THE SAME

US20260128287A1US 20260128287 A1US20260128287 A1US 20260128287A1US-20260128287-A1

Abstract

Disclosed are a positive electrode for a rechargeable lithium battery, and a rechargeable lithium battery including the positive electrode. 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 that includes 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

  • Sungwook DOO

Assignees

  • SAMSUNG SDI CO., LTD.

Dates

Publication Date
20260507
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 including a lithium iron phosphate-based compound; and a second positive electrode active material layer on the first positive electrode active material layer and that comprises 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 as claimed in claim 1 , wherein the lithium iron phosphate-based compound is represented by one of Chemical Formula 1 and Chemical Formula 2; wherein, in Chemical Formula 1, 0.9≤a1≤1.5, 0≤x1≤0.4, and M 1 comprises at least one of Al, Ca, Ce, Cr, Cu, La, Mg, Mn, Mo, Nb, Ni, Sn, Sr, Ti, V, W, Y, Zn, and Zr, wherein, in Chemical Formula 2, 0.9≤a2≤1.5, 0.1≤x2≤0.9, 0≤y2<0.9, and M 2 comprises 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 as claimed in claim 1 , wherein: the first positive electrode active material comprises one of first particles, second particles, and a mixture thereof, the first particles comprise secondary particles formed by agglomeration of a plurality of primary particles, and the second particles are in a form of single particles.
  4. 4 . The positive electrode as claimed in claim 3 , wherein: an average particle diameter (D 50 ) of the secondary particles of the first particles is in a range of about 5 μm to about 20 μm, an average particle diameter (D 50 ) of the primary particles forming the secondary particles is in a range of about 0.1 μm to about 2 μm, and an average particle diameter (D 50 ) of the single particles of the second particles is in a range of about 0.5 μm to about 5 μm.
  5. 5 . The positive electrode as claimed in claim 3 , wherein an amount of the first particles is in a range of about 20 wt % to about 100 wt %; and an amount of the second particles is in a range of about 0 wt % to about 80 wt % based on 100 wt % of the first positive electrode active material.
  6. 6 . The positive electrode as claimed in claim 3 , wherein the first positive electrode active material further comprises at least one of: a carbon coating layer formed on a surface of the secondary particles of the first particles, a carbon coating layer formed on a surface of the primary particles forming the secondary particles of the first particles, and a carbon coating layer formed on a surface of the single particles of the second particles.
  7. 7 . The positive electrode as claimed in claim 6 , wherein: the carbon coating layer is included in an amount in a range of about 0.1 wt % to about 3.9 wt % based on 100 wt % of the first particles, and the carbon coating layer is included in an amount in a range of about 0.1 wt % to about 3.9 wt % based on 100 wt % of the second particles.
  8. 8 . The positive electrode as claimed in claim 1 , wherein the lithium nickel-based composite oxide of the second positive electrode active material is represented by Chemical Formula 3: wherein, in 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, M 3 and M 4 each independently comprises 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 comprises one or more of F, P, and S.
  9. 9 . The positive electrode as claimed in claim 1 , wherein the lithium nickel-based composite oxide of the second positive electrode active material comprises nickel in an amount that is greater than or equal to about 80 mol % based on 100 mol % of a total metal excluding lithium nickel.
  10. 10 . The positive electrode as claimed in claim 1 , wherein the second positive electrode active material comprises at least one of large particles having an average particle diameter (D 50 ) in a range of about 9 μm to about 20 μm, and small particles having an average particle diameter (D 50 ) in a range of about 1 μm to about 8 μm.
  11. 11 . The positive electrode as claimed in claim 10 , wherein: the second positive electrode active material comprises both the large particles and the small particles, and the large particles and the small particles are mixed in a weight ratio in a range of about 20:80 to about 95:5.
  12. 12 . The positive electrode as claimed in claim 1 , wherein the lithium manganese-based oxide is represented by Chemical Formula 6; 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 comprises 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 comprises one or more of F, P, and S.
  13. 13 . The positive electrode as claimed in claim 1 , wherein: the third positive electrode active material comprises secondary particles formed by agglomeration of one of a plurality of primary particles, single particles, and a mixture thereof, an average particle diameter (D 50 ) of the secondary particles is in a range of about 5 μm to about 15 μm, and an average particle diameter (D 50 ) of the single particles is in a range of about 0.1 μm to about 10 μm.
  14. 14 . The positive electrode as claimed in 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 about 10:90 to about 90:10.
  15. 15 . The positive electrode as claimed in claim 1 , wherein: in a total 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 a range of about 10 wt % to about 70 wt %, the second positive electrode active material is included in an amount in a range of about 10 wt % to about 50 wt %, and the third positive electrode active material is included in an amount in a range of about 20 wt % to about 80 wt %, based on a total of 100 wt % 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 as claimed in claim 1 , wherein a manganese content in a total of the first positive electrode active material layer and the second positive electrode active material layer is in a range of about 30 mol % to about 70 mol % based on 100 mol % of a total metal excluding lithium.
  17. 17 . The positive electrode as claimed in claim 1 , wherein: the first positive electrode active material layer further comprises at least one of a first binder and a first conductive material, and the second positive electrode active material layer further comprises at least one of a second binder and a second conductive material.
  18. 18 . The positive electrode as claimed in claim 1 , wherein: a loading level of the first positive electrode active material layer is in a range of about 5 mg/cm 2 to about 25 mg/cm 2 , and a loading level of the second positive electrode active material layer is in a range of about 5 mg/cm 2 to about 25 mg/cm 2 .
  19. 19 . The positive electrode as claimed in 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 about 2.0 g/cc to about 4.0 g/cc.
  20. 20 . A rechargeable lithium battery comprising: the positive electrode as claimed in claim 1 , a negative electrode, and an electrolyte.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Korean Patent Application No. 10-2024-0155568 filed with the Korean Intellectual Property Office on Nov. 5, 2024, the entire contents of which are incorporated herein by reference. BACKGROUND 1. Field A positive electrode for a rechargeable lithium battery, and a rechargeable lithium battery including the positive electrode are disclosed. 2. Description of the Related Art Rechargeable lithium batteries, which are easy to carry as well as achieve high energy density, are widely used as power sources for mobile information terminals such as, e.g., smart phones, laptops, and the like. Obtaining rechargeable lithium batteries with high safety and high capacity for the use as power sources for hybrid vehicles and electric vehicles or for storing electric power may be advantageous. In addition, because rechargeable lithium batteries are typically required to achieve rapid charging characteristics as well as high safety, a low-cost lithium iron phosphate-based compound may constitute a positive electrode active material. However, lithium iron phosphate-based compounds have limitations in exhibiting high energy density and high capacity. There have been attempts to form electrode plates by mixing lithium nickel-based composite oxides and lithium iron phosphate-based compounds in order to achieve high energy density, high stability, and high capacity while also increasing price competitiveness. However, when manufacturing an electrode plate by mixing a lithium nickel-based composite oxide and a lithium iron phosphate-based compound, separation of the operating voltage may occur, which reduces the capacity and deteriorates cycle-life characteristics of the battery due to deterioration of the positive electrode active material. SUMMARY Some example embodiments include a positive electrode for a rechargeable lithium battery, which improves rate capability and cycle-life characteristics without separation of operating voltages, by mixing three types of positive electrode active materials and adopting a double-layer structure, and a rechargeable lithium battery including the positive electrode. 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 structurally stable, low-cost lithium iron phosphate-based positive electrode active material, a lithium nickel-based positive electrode active material having high capacity and energy density, and a low-cost lithium manganese-based positive electrode active material exhibiting capacity at a voltage of about 4 V, and adopts a double-layer structure so that an operating voltage may not be separated, and rate capability and cycle-life characteristics may be improved. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 4 are schematic views showing rechargeable lithium batteries according to some example embodiments. FIG. 5 is a graph showing the voltage profile according to the capacity at the time of the first charge and discharge for the rechargeable lithium battery cell of Comparative Example 4 and the rechargeable lithium battery cell of Comparative Example 5. FIG. 6 is a schematic view showing a positive electrode according to some example embodiments. DETAILED DESCRIPTION Hereinafter, example embodiments are described in detail so that those of ordinary skill in the art can readily implement the example embodiments. However, this disclosure may be embodied in many different forms and is not construed as limited to the example embodiments set forth herein. The terminology used herein is used to describe example embodiments only, and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly dictates otherwise. As used herein, “combination thereof” indicates a mixture, a laminate, a composite, a copolymer, an alloy, a blend, a reaction product, and the like of the constituents. Herein, it should be understood that terms such as “comprises,” “includes,” or “have” are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but does not preclude the possibility of