Positive Electrode Active Material For Lithium Secondary Battery, Method of Preparing the same, and Positive Electrode for Lithium Secondary Battery and Lithium Secondary Battery which include the positive Electrode Active Material

Patent metadata

Field	Value
Publication number	US-2021234155-A1
Application number	US-201917050553-A
Country	US
Kind code	A1
Filing date	May 10, 2019
Priority date	May 11, 2018
Publication date	Jul 29, 2021
Grant date	—

Abstract

The present invention relates to a positive electrode active material, which includes a lithium transition metal oxide having an average composition represented by Formula 1 in which a cobalt content in the lithium transition metal oxide is less than a manganese content, wherein at least one of nickel, cobalt, and manganese in the lithium transition metal oxide has a concentration gradient that gradually changes from a center of a particle to a surface thereof, the positive electrode active material is in the form of a secondary particle formed by agglomeration of primary particles, and a ratio in which angles between c-axis directions, which are measured at at least 8 points on a surface of the positive electrode active material by TEM analysis, and a growth direction of the particle at the measuring point satisfy 85° to 95° is 60% or more, a method of preparing the positive electrode active material, and a positive electrode for a lithium secondary battery and a lithium secondary battery which include the positive electrode active material:
Li 1+a Ni x Co y Mn z M 1 w O 2   [Formula 1]
in Formula 1, 0≤a≤0.3, 0.65≤x<1, 0<y≤0.35, 0<z≤0.35, 0≤w≤0.02, and y<z, and M 1 includes at least one selected from the group consisting of aluminum (Al), zirconium (Zr), magnesium (Mg), zinc (Zn), yttrium (Y), iron (Fe), and titanium (Ti).

First claim

1 . A positive electrode active material comprising:
a lithium transition metal oxide having an average composition represented by Formula 1 in which a cobalt content in the lithium transition metal oxide is less than a manganese content, wherein at least one of nickel, cobalt, or manganese in the lithium transition metal oxide has a concentration gradient that gradually changes from a center of a particle to a surface thereof, the positive electrode active material is in a form of a secondary particle formed by agglomeration of primary particles, and a ratio in which angles between c-axis directions, which are measured at at least 8 points on a surface of the positive electrode active material by transmission electron microscope (TEM) analysis, and a growth direction of the particle at the measuring point satisfy 85° to 95° is 60% or more:
Li 1+a Ni x Co y Mn z M 1 w O 2   [Formula 1]

wherein, in Formula 1, 0≤a≤0.3, 0.65≤x<1, 0<y≤0.35, 0<z≤0.35, 0≤w≤0.02, and y<z, and M 1 comprises at least one selected from the group consisting of aluminum (Al), zirconium (Zr), magnesium (Mg), zinc (Zn), yttrium (Y), iron (Fe), and titanium (Ti).

2 . The positive electrode active material of claim 1 , wherein a molar ratio of cobalt:manganese in the lithium transition metal oxide is in a range of greater than 1:1 to 1:10 or less.

3 . The positive electrode active material of claim 1 , wherein the positive electrode active material comprises columnar-structured primary particles, which are grown in a surface direction from a center of the positive electrode active material, in a surface portion.

4 . The positive electrode active material of claim 1 , wherein the lithium transition metal oxide represented by Formula 1 comprises the cobalt in an amount of greater than 0 mol % to 15 mol % or less based on the total number of moles of transition metals excluding lithium.

5 . The positive electrode active material of claim 1 , wherein the lithium transition metal oxide represented by Formula 1 comprises the manganese in an amount of 20 mol % or more to less than 35 mol % based on the total number of moles of transition metals excluding lithium.

6 . A method of preparing a positive electrode active material, the method comprising:
preparing a first transition metal-containing solution including a nickel raw material and a second transition metal-containing solution having a transition metal concentration different from that of the first transition metal-containing solution and including the nickel raw material, a cobalt raw material, and a manganese raw material; preparing a positive electrode active material precursor by mixing the first transition metal-containing solution and the second transition metal-containing solution while gradually changing a mixing ratio of the first transition metal-containing solution to the second transition metal-containing solution; and mixing the positive electrode active material precursor with a lithium-containing raw material to form a mixture and sintering the mixture to synthesize the positive electrode active material, wherein the preparing of the positive electrode active material precursor is controlled such that a pH is gradually decreased as a nickel content in the mixed solution is reduced.

7 . The method of claim 6 , wherein a molar ratio of nickel:cobalt:manganese in the first transition metal-containing solution is in a range of 80 to 100:0 to 10:0 to 20.

8 . The method of claim 6 , wherein a molar ratio of nickel:cobalt:manganese in the second transition metal-containing solution is in a range of 50 to 80:10 to 30:10 to 35.

9 . The method of claim 6 , wherein the pH is gradually decreased within a range of 13 to 9.

10 . The method of claim 6 , further comprising a doping element M 1 raw material, wherein M 1 comprises at least one selected from the group consisting of Al, Zr, Mg, Zn, Y, Fe, and Ti, during the mixing of the positive electrode active material precursor with the lithium-containing raw material.

11 . A positive electrode for a lithium secondary battery, the positive electrode comprising the positive electrode active material of claim 1 .

12 . A lithium secondary battery comprising the positive electrode of claim 11 .

13 . The positive electrode active material of claim 3 , wherein the columnar-structure primary particles have a column-structure having an aspect ratio of 2 to 5.

Assignees

• Lg Chemical Ltd

Inventors

• Jeong Myung Gi
• Son Se Hwan
• Cho Seung Beom
• Choi Sang Soon

Classifications

• H01M4/0471

  involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis · CPC title

• C01G53/82 Primary

  Compounds containing nickel, with or without oxygen or hydrogen, and containing two or more other elements · CPC title

• C01P2004/04

  obtained by TEM, STEM, STM or AFM · CPC title

• C01P2006/40

  Electric properties · 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