Positive electrode active material for lithium secondary battery, method of preparing the same and lithium secondary battery including the same

Patent metadata

Field	Value
Publication number	US-2017309910-A1
Application number	US-201515515728-A
Country	US
Kind code	A1
Filing date	Oct 2, 2015
Priority date	Oct 2, 2014
Publication date	Oct 26, 2017
Grant date	—

Abstract

The present invention provided a positive electrode active material for a lithium secondary battery including lithium cobalt oxide particles. The lithium cobalt oxide particles include lithium deficient lithium cobalt oxide having Li/Co molar ratio of less than 1, belongs to an Fd-3m space group, and having a cubic crystal structure, in surface of the particle and in a region corresponding to a distance from 0% to less than 100% from the surface of the particle relative to a distance (r) from the surface to the center of the particle. In the positive electrode active material for a lithium secondary battery according to the present invention, the intercalation and deintercalation of lithium at the surface of a particle may be easy, and the output property and rate characteristic may be improved when applied to a battery.

First claim

1 . A positive electrode active material for a lithium secondary battery, comprising lithium cobalt oxide particles,
wherein the lithium cobalt oxide particle has a core-shell structure comprising a core part and a shell part provided on a surface of the core part, wherein the lithium cobalt oxide particles comprise lithium deficient lithium cobalt oxide on a surface of a particle and in a region corresponding to a distance from 0% to less than 100% from the surface of the particle relative to a distance (r) from the surface to the center of the particle, the lithium deficient lithium cobalt oxide having a Li/Co molar ratio of less than 1, belongs to an Fd-3m space group, and having a cubic crystal structure, and wherein the shell part comprises lithium deficient lithium cobalt oxide comprises first lithium cobalt oxide of the following Formula 1, and the core part comprises second lithium cobalt oxide of the following Formula 2:
Li 1-a CoM x O 2   [Formula 1]

Li b COM′ y O 2   [Formula 2]

In Formula 1 and 2, M and M′ each independently comprises at least one metal element selected from the group consisting of W, Mo, Zr, Ti, Mg, Ta, Al, Fe, V, Cr, Ba, Ca, and Nb, and a, b, x, and y satisfies the following relations of 0<a≦0.05, 1≦b≦1.2, 0≦x≦0.02, and 0≦y≦0.02.

2 . (canceled)

3 . (canceled)

4 . The positive electrode active material of claim 1 , wherein
the first lithium cobalt oxide belongs to an Fd-3m space group and has a cubic crystal structure, and the second lithium cobalt oxide has a layered crystal structure.

5 . The positive electrode active material of claim 1 , wherein the shell part is a region corresponding to a distance from 0% to 99% from the surface relative to a distance from the surface to the center of the lithium cobalt oxide particle.

6 . The positive electrode active material of claim 1 , wherein the core part and the shell part has a thickness ratio from 1:0.01 to 1:0.1.

7 . The positive electrode active material of claim 1 , wherein the core part and the shell part each comprises lithium distributed with an increasing concentration gradient toward the center of the lithium cobalt oxide particle.

8 . The positive electrode active material of claim 1 , wherein the concentration gradient slope of the lithium in the core part and the concentration gradient slope of the lithium in the shell part have the same or different slope values.

9 . The positive electrode active material of claim 1 , wherein the core part has higher lithium concentration than the shell part, and at least one of the core part and the shell part comprises the lithium present with one concentration value in a corresponding region.

10 . The positive electrode active material of claim 1 , wherein
the lithium is distributed with a gradually increasing concentration gradient from the surface to the center of the lithium cobalt oxide particle, and in Formula 1 and 2, a is gradually decreasing toward the center of the particle within a range of 0<a≦0.05, and b is gradually increasing toward the center of the particle within a range of 1≦b≦1.2.

11 . The positive electrode active material of claim 1 , wherein the positive electrode active material has a monolith structure with an average particle diameter from 3 to 50 μm.

12 . The positive electrode active material of claim 1 , having an inflection point within a voltage range from 4.0 V to 4.2 V when measuring a voltage profile according to charging and discharging.

13 . A method of preparing the positive electrode active material for a lithium secondary battery according to claim 1 , the method comprising:
preparing second lithium cobalt oxide particles by mixing a cobalt raw material and a lithium raw material in amounts satisfying a molar ratio of 1≦Li/Co≦1.2, and first heating; and second heating the second lithium cobalt oxide particles, more than once.

14 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 13 , wherein a metal-containing raw material comprising at least one metal element selected from the group consisting of W, Mo, Zr, Ti, Mg, Ta, Al, Fe, V, Cr, Ba, Ca, and Nb is further included during mixing the cobalt raw material and the lithium raw material in the preparing of the second lithium cobalt oxide particles.

15 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 13 , wherein the first heating is conducted by heating at a temperature from 800° C. to 1,100° C. in the atmosphere or an oxygen atmosphere.

16 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 13 , wherein the second heating is conducted by heating at a temperature from 800° C. to 1,100° C. in the atmosphere or an oxygen atmosphere.

17 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 13 , wherein the second heating is conducted twice at a temperature from 800° C. to 1,100° C., and the temperature during each heating is the same or different.

18 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 13 , further comprising adding a cobalt raw material, or a cobalt raw material and a lithium raw material during the second heating.

19 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 13 , further comprising adding a cobalt raw material and a lithium raw material in amounts satisfying the following relation of 0.95<Li/Co molar ratio<1 during the second heating.

20 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 13 , further comprising adding a metal-containing raw material including at least one metal element selected from the group consisting of W, Mo, Zr, Ti, Mg, Ta, Al, Fe, V, Cr, Ba, Ca, and Nb during the second heating.

21 .- 26 . (canceled)

Assignees

• Lg Chemical Ltd

Inventors

• Jo Chi Ho
• Ryu Ji Hoon
• Kang Min Suk
• Shin Sun Sik
• Jung Wang Mo

Classifications

• H01M4/366

  as layered products · CPC title

• H01M2220/20

  Batteries in motive systems, e.g. vehicle, ship, plane · CPC title

• C01G51/42

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

• C01P2002/76

  by a space-group or by other symmetry indications · CPC title

• C01P2004/04

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