Positive Electrode Active Material for Secondary Battery, Method for Preparing the Same, and Lithium Secondary Battery Including the Same

Patent metadata

Field	Value
Publication number	US-2020220173-A1
Application number	US-201816647307-A
Country	US
Kind code	A1
Filing date	Aug 29, 2018
Priority date	Sep 19, 2017
Publication date	Jul 9, 2020
Grant date	—

Abstract

A positive electrode active material for a secondary battery is provided. The positive electrode active material being a lithium cobalt-based oxide includes a doping element M. A lithium cobalt-based oxide particle containing the doping element M in an amount of 3,000 ppm or more, wherein in a bulk portion corresponding to 90% of a core side among the radius from a core of the particle to a surface thereof, the doping element M in the lithium cobalt-based oxide particle is contained at a constant concentration, and in a surface portion from the surface of the particle to 100 nm in a core direction, the doping element M is contained at a concentration equal to or higher than that in the bulk portion and has a concentration in which the concentration thereof is gradient gradually decreased in the core direction from the surface of the particle.

First claim

1 . A positive electrode active material for a secondary battery, comprising a lithium cobalt-based oxide including a doping element M, wherein a lithium cobalt-based oxide particle contains the doping element M in an amount of 3,000 ppm or more,
wherein in a bulk portion corresponding to 90% of a core side among a radius from a core of the lithium cobalt-based particle to a surface thereof, the doping element M in the lithium cobalt-based oxide particle is contained at a constant concentration, and wherein in a surface portion from a surface of the lithium cobalt-based particle to 100 nm in a core direction, the doping element M is contained at a concentration equal to or higher than that in the bulk portion, and has a concentration gradient in which the concentration thereof is gradually decreased in the core direction from the surface of the lithium cobalt-based oxide particle.

2 . The positive electrode active material for a secondary battery of claim 1 , wherein the lithium cobalt-based oxide particle contains the doping element M in the amount of 5,000-8,000 ppm.

3 . The positive electrode active material for a secondary battery of claim 1 , wherein the lithium cobalt-based oxide particle contains 30% or more of a total amount of the doping element M in the surface portion from the surface of the lithium cobalt-oxide particle to 100 nm in the core direction.

4 . The positive electrode active material for a secondary battery of claim 1 , wherein the surface portion has the concentration gradient in which the concentration of the doping element M is gradually decreased from the surface of the lithium cobalt-based oxide particle to 10 to 50 nm in the core direction of the lithium cobalt-based oxide particle.

5 . The positive electrode active material for a secondary battery of claim 1 , wherein the doping element M is at least one selected from the group consisting of Al, Ti, Zr, Mg, Nb, Ba, Ca and Ta.

6 . The positive electrode active material for a secondary battery of claim 1 , wherein the doping element M is Al, Ti or Mg.

7 . The positive electrode active material for a secondary battery of claim 1 , wherein the lithium cobalt-based oxide particle is represented by Formula 1 below,
Li a Co (1-x) M x O 2   [Formula 1]

wherein, 0.95≤a≤1.05, 0<x≤0.2, and M is at least one selected from the group consisting of Al, Ti, Zr, Mg, Nb, Ba, Ca and Ta.

8 . The positive electrode active material for a secondary battery of claim 1 , further comprising a coating layer on the surface of the lithium cobalt-based oxide particle,
wherein the coating layer comprises at least one oxide selected from the group consisting of Mg, Ti, Fe, Cu, Ca, Ba, Sn, Sb, Na, Zn, Si, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sc, Ce, Pr, Nd, Gd, Dy, Yb, Er, Co, Al, Ga and B.

9 . The positive electrode active material for a secondary battery of claim 1 , wherein the lithium cobalt-based oxide has a molar ratio of lithium to a metal element excluding lithium of 0.98 to 1.1.

10 . A method for preparing a positive electrode active material for a secondary battery, comprising:
preparing a Co 3 O 4 or CoOOH precursor doped with a doping element M in an amount of 1,000 ppm or more; mixing the doped Co 3 O 4 or CoOOH precursor with a lithium raw material and performing a first heat treatment to prepare a lithium cobalt-based oxide including the doping element M; and mixing the lithium cobalt-based oxide with a raw material of the doping element M and performing a second heat treatment to prepare a lithium cobalt-based oxide, wherein a surface of the lithium cobalt-based oxide is additionally doped with the doping element M.

11 . The method of claim 10 , wherein the preparing the doped Co 3 O 4 or CoOOH precursor doped with the doping element M in an amount of 1,000 ppm or more comprises:
preparing a precursor forming solution including a cobalt-containing starting material and the raw material of the doping element M; and subjecting the precursor forming solution to coprecipitation reaction.

12 . The method of claim 10 , wherein the precursor is doped with the doping element M in an amount of 3,000 to 6,000 ppm.

13 . The method of claim 10 , wherein the lithium cobalt-based oxide including the doping element M prepared after the first heat treatment comprises the doping element M at a constant concentration in the lithium cobalt-based oxide particle.

14 . The method of claim 10 , wherein the raw material of the doping element M is mixed in an amount of 0.05 to 0.5 parts by weight, with respect to 100 parts by weight of the lithium cobalt-based oxide.

15 . The method of claim 10 , wherein the second heat treatment is performed at 800 to 950° C.

16 . The method of claim 10 , wherein the lithium cobalt-based oxide the surface of which is additionally doped with the doping element M and which is prepared after the second heat treatment comprises the doping element M in an amount of 3,000 ppm or more,
wherein in a bulk portion corresponding to 90% of a core side among a radius from a core of the lithium cobalt-based oxide particle to a surface thereof, the doping element M is contained at a constant concentration, and in a surface portion from the surface of the lithium cobalt-based oxide particle to 100 nm in a core direction, the doping element M is contained at a concentration equal to or higher than that in the bulk portion and has a concentration gradient in which the concentration thereof is gradually decreased in the core direction from the surface of the particle.

17 . The method of claim 10 , wherein the doping element M is at least one selected from the group consisting of Al, Ti, Zr, Mg, Nb, Ba, Ca and Ta.

18 . The method of claim 10 , wherein the performing a heat treatment to prepare the lithium cobalt oxide the surface of the lithium cobalt-based oxide is additionally doped with the doping element M comprises further mixing a cobalt-containing starting material when the lithium cobalt-based oxide is mixed with the raw material of the doping element M.

19 . A positive electrode for a secondary battery comprising the positive electrode active material according to claim 1 .

20 . A lithium secondary battery comprising the positive electrode according to claim 19 .

Assignees

• Lg Chemical Ltd

Inventors

• Jo Chi Ho
• You Min Kyu
• Park Sung Bin
• Hur Hyuck
• Hwang Jin Tae
• Jung Wang Mo

Classifications

• C01G51/42 Primary

  containing alkali metals, e.g. LiCoO2 · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/525 Primary

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title

• H01M4/366

  as layered products · CPC title

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title