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US-12620577-B2 - Positive electrode active material and lithium secondary battery comprising the same

US12620577B2US 12620577 B2US12620577 B2US 12620577B2US-12620577-B2

Abstract

The present invention relates to a positive electrode active material, and a lithium secondary battery comprising a positive electrode including the positive electrode active material.

Inventors

  • Moon Ho Choi
  • Gyeong Jae HEO
  • Hyun Jong YU
  • Seung Hyun Choi

Assignees

  • ECOPRO BM CO., LTD.

Dates

Publication Date
20260505
Application Date
20190820
Priority Date
20180822

Claims (9)

  1. 1 . A positive electrode active material, comprising: a single primary particle comprising both a first composite oxide and a second composite oxide, which are present in a state of forming one solid solution, wherein: the first composite oxide enables lithium intercalation and deintercalation and has a first crystal structure belonging to a hexagonal crystal system; and the second composite oxide presents on at least a part of the surface of the first composite oxide and has a second crystal structure having at least one crystal structure selected from monoclinic, triclinic and cubic systems, and wherein the first composite oxide is represented by Formula 2 below: Li w Ni 1-(x+y+z) Co x M3 y M4 z O 2 [Formula 2] (Here, M3 is Al, M4 is at least one selected from Al, Ti, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, 0.5≤w≤1.2, 0.01≤x≤0.50,0.01≤y≤0.20, and 0.001≤z≤0.20), and the second composite oxide is represented by Formula 1 below: Li a Ni b M2 c O d [Formula 1] (Here, M2 is at least one selected from Al, Zr, Mg, V, B, Mo, Zn, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, 0≤a≤6, 0<b≤2, 0<c≤2, and 4≤d≤8), wherein the positive electrode active material exhibits both of a diffraction peak pattern specific for the first composite oxide and a diffraction peak pattern specific for the second composite oxide, wherein, in X-ray photoelectron spectroscopy (XPS) analysis for the solid solution, peaks corresponding to W4f 7/2 are present in a range of 34.0 eV to 35.0 eV and in a range exceeding 35.0 eV, respectively, wherein, in X-ray photoelectron spectroscopy (XPS) analysis for the solid solution, peaks corresponding to W4f 5/2 are present in a range of 36.0 eV to 37.0 eV and in a range exceeding 37.0 eV, respectively, wherein the single primary particle is core-shell particle, comprising: a core including the first composite oxide; and a shell layer including the second composite oxide, wherein the average diameter of the core-shell particle is 0.1 to 6.0 μm, and the thickness of the shell layer is 20 nm or less.
  2. 2 . The positive electrode active material of claim 1 , wherein the second composite oxide present in the shell layer is a lithium-rich metal oxide.
  3. 3 . The positive electrode active material of claim 1 , wherein the positive electrode active material comprises the core-shell particles and a secondary particle formed by aggregating the core-shell particles.
  4. 4 . The positive electrode active material of claim 1 , wherein the solid solution is represented by Formula 3 below: Li a Ni b M2 c O d —Li w Ni 1-(x+y+z) Co x M3 y M4 z O 2 [Formula 3] (Here, M2 is at least one selected from Al, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, M3 is Al, M4 is at least one selected from Al, Ti, Zr, Mg, V, B, Mo, Zn, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, 0≤a≤6,0<b≤2,0<c≤2,4≤d≤8,0.5≤w≤1.5, 0.01≤x≤0.50, 0.01≤y≤0.20, and 0.001≤z≤0.20).
  5. 5 . The positive electrode active material of claim 4 , wherein M2 is the same as M4 or a part of M4.
  6. 6 . The positive electrode active material of claim 3 , further comprising: a coating layer covering at least a part of the secondary particle, wherein the coating layer includes an alloy oxide represented by Formula 4 below: Li e M5 f O g [Formula 4] (Here, M5 is at least one selected from Mn, Al, Ti, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ca, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, 0≤e≤6, 0<f≤6, and 0<g≤10).
  7. 7 . A lithium secondary battery comprising a positive electrode including the positive electrode active material of claim 1 .
  8. 8 . A positive electrode active material, comprising: a single primary particle comprising both a first composite oxide and a second composite oxide, which are present in a state of forming one solid solution, wherein: the first composite oxide enables lithium intercalation and deintercalation and has a first crystal structure belonging to a hexagonal crystal system; and the second composite oxide presents on at least a part of the surface of the first composite oxide and has a second crystal structure having at least one crystal structure selected from monoclinic, triclinic and cubic systems, and wherein the first composite oxide is represented by Formula 2 below: Li w Ni 1-(x+y+z) Co x M3 y M4 2 O 2 [Formula 2] (Here, M3 is Al, M4 is at least one selected from Al, Ti, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, 0.5≤w≤1.2, 0.01≤x≤0.50, 0.01≤y≤0.20, and 0.001≤z≤0.20), and the second composite oxide is represented by Formula 1 below: Li a Ni b M2 c O d [Formula 1] (Here, M2 is W or a combination of W and at least one selected from Al, Zr, Mg, V, B, Mo, Zn, Ba, Ta, Fe, Cr, Sn, Hf, Ce, Nd and Gd, 0≤a≤6, 0<b≤2, 0<c≤2, and 4≤d≤8), wherein the positive electrode active material exhibits both of a diffraction peak pattern specific for the first composite oxide and a diffraction peak pattern specific for the second composite oxide, wherein, in X-ray photoelectron spectroscopy (XPS) analysis for the solid solution, peaks corresponding to W4f 7/2 are present in a range of 34.0 eV to 35.0 eV and in a range exceeding 35.0 eV, respectively, wherein, in X-ray photoelectron spectroscopy (XPS) analysis for the solid solution, peaks corresponding to W4f 5/2 are present in a range of 36.0 eV to 37.0 eV and in a range exceeding 37.0 eV, respectively, wherein the single primary particle is core-shell particle, comprising: a core including the first composite oxide; and a shell layer including the second composite oxide, wherein the average diameter of the core-shell particle is 0.1 to 6.0 μm, and the thickness of the shell layer is 20 nm or less.
  9. 9 . A positive electrode active material, comprising: a single primary particle comprising both a first composite oxide and a second composite oxide, which are present in a state of forming one solid solution, wherein: the first composite oxide enables lithium intercalation and deintercalation and has a first crystal structure belonging to a hexagonal crystal system; and the second composite oxide presents on at least a part of the surface of the first composite oxide and has a second crystal structure has at least one crystal structure selected from monoclinic, triclinic and cubic systems, and wherein the first composite oxide is represented by Formula 2 below: Li w Ni 1-(x+y+z) Co x M3 y M4 z O 2 [Formula 2] (Here, M3 is at least one selected from Mn and Al, M4 is at least one selected from Mn, Al, Ti, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, 0.5≤w≤1.2, 0.01≤x≤0.50,0.01≤y≤0.20, and 0.001≤z≤0.20), the second composite oxide is represented by Formula 1 below: Li a Ni b M2 c O d [Formula 1] (Here, M2 is at least one selected from Al, Zr, Mg, V, B, Mo, Zn, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, 0≤a≤6, 0<b≤2, 0<c≤2, and 4≤d≤8), and wherein the positive electrode active material exhibits both of a diffraction peak pattern specific for the first composite oxide and a diffraction peak pattern specific for the second composite oxide, wherein, in X-ray photoelectron spectroscopy (XPS) analysis for the solid solution, peaks corresponding to W4f 7/2 are present in a range of 34.0 eV to 35.0 eV and in a range exceeding 35.0 eV, respectively, wherein, in X-ray photoelectron spectroscopy (XPS) analysis for the solid solution, peaks corresponding to W4f 5/2 are present in a range of 36.0 eV to 37.0 eV and in a range exceeding 37.0 eV, respectively, wherein the single primary particle is core-shell particle, comprising: a core including the first composite oxide; and a shell layer including the second composite oxide, wherein the average diameter of the core-shell particle is 0.1 to 6.0 μm, and the thickness of the shell layer is 20 nm or less.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to and the benefit of Korean Patent Application No. 10-2018-0098186, filed on Aug. 22, 2018, Korean Patent Application No. 10-2018-0111347, filed on Sep. 18, 2018, Korean Patent Application No. 10-2019-0062986, filed on May 29, 2019, and Korean Patent Application No. 10-2019-0082546, filed on Jul. 9, 2019, the disclosure of which is incorporated herein by reference in its entirety. BACKGROUND 1. Field of the Invention The present invention relates to a positive electrode active material, and a lithium secondary battery comprising a positive electrode including the positive electrode active material. 2. Discussion of Related Art Batteries store electrical power by using materials facilitating an electrochemical reaction with a positive electrode and a negative electrode. As a representative example of such batteries, there is a lithium secondary battery storing electrical energy due to a difference in chemical potential when lithium ions are intercalated/deintercalated into/from a positive electrode and a negative electrode. The lithium secondary battery uses materials enabling reversible intercalation/deintercalation of lithium ions as positive electrode and negative electrode active materials, and is produced by charging an organic electrolyte solution or a polymer electrolyte solution between the positive electrode and the negative electrode. A lithium composite oxide is used as a positive electrode active material of the lithium secondary battery, and composite oxides such as LiCoO2, LiMn2O4, LiNiO2, LiMnO2, etc. are being studied. Among the positive electrode active materials, while LiCoO2 is most widely used due to excellent lifespan characteristics and charge/discharge efficiency, it is expensive because of the resource limit of cobalt used as a raw material, and has a disadvantage that price competitiveness is limited. Lithium manganese oxides such as LiMnO2, LiMn2O4, etc. have advantages of excellent thermal safety and low costs, but also have problems of small capacity and poor high-temperature characteristics. In addition, while a LiNiO2-based positive electrode active material exhibits a battery characteristic of high discharge capacity, due to cation mixing between Li and a transition metal, it is difficult to synthesize the LiNiO2-based positive electrode active material, thereby causing a greater problem in rate characteristic. In addition, depending on the intensification of such cation mixing, a large amount of Li by-products is generated, and since most of the Li by-products consist of a compound of LiOH and Li2CO3, they become a cause of gelation in preparation of a positive electrode paste and gas generation according to charge/discharge progression after the preparation of an electrode. Residual Li2CO3 increases the swelling phenomenon of a cell and thus reduces cycles and also leads to the swelling of a battery. SUMMARY To solve various problems of a conventional positive electrode active material for a lithium secondary battery, the present invention is directed to providing a positive electrode active material which is improved in structural stability and conductivity of lithium ions. The present invention is also directed to providing a positive electrode active material which includes different types of composite oxides defined herein, and thereby is improved in high temperature storage stability and lifespan characteristics. The present invention is also directed to providing a lithium secondary battery comprising a positive electrode including the positive electrode active material defined herein. The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by the following description and more clearly understood by exemplary embodiments of the present invention. In addition, it will be readily apparent that the objects and advantages of the present invention may be realized by means indicated in the claims and a combination thereof. One aspect of the present invention may provide a positive electrode active material which includes a first composite oxide enabling lithium intercalation and deintercalation and a second composite oxide present on at least a part of the surface of the first composite oxide and in a state of forming a solid solution with the first composite oxide. Here, the second composite oxide may be represented by Formula 1 below. LiaM1bM2cOd  [Formula 1] (Here, M1 is at least one selected from Ni, Mn, Co, Cu, Nb, Mo, Al, Zn, Mg, Ce and Sn, M2 is at least one selected from Mn, Al, Ti, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, M1 and M2 are different from each other, 0≤a≤6, 0≤b≤2, 0≤c≤2, and 4≤d≤8) Another aspect of the present invention may provide a lithium secondary battery comprising a positive electrode including the positive electrode activ