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-2017222225-A1
Application number	US-201515515447-A
Country	US
Kind code	A1
Filing date	Oct 2, 2015
Priority date	Oct 2, 2014
Publication date	Aug 3, 2017
Grant date	—

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery, and a lithium secondary battery including the same, and the positive electrode active material includes lithium cobalt oxide particles. The lithium cobalt oxide particles include lithium cobalt oxide having a Li/Co molar ratio of less than 1 in the particles. Good rate property and life property may be obtained without worrying on the deterioration of initial capacity property.

First claim

1 . A positive electrode active material for a lithium secondary battery, comprising lithium cobalt oxide particles,
wherein the lithium cobalt oxide particle comprise a lithium deficient lithium cobalt oxide having a Li/Co molar ratio of less than 1 in the particle, wherein the lithium cobalt oxide particle has a core-shell structure comprising a core part and a shell part: the core part comprising the first lithium cobalt oxide of the following Formula 1; and the shell part provided on a surface of the core part and comprising a 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 satisfy the following relations of 0<a≦0.05, 1≦b≦1.2, 0≦x≦0.02, and 0≦y≦0.02.

2 . The positive electrode active material for a lithium secondary battery of claim 1 , wherein the lithium deficient lithium cobalt oxide belongs to an Fd-3m space group and has a cubic crystal structure.

3 - 4 . (canceled)

5 . The positive electrode active material for a lithium secondary battery 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.

6 . The positive electrode active material for a lithium secondary battery of claim 1 , wherein the core part is a region corresponding to a distance from 0% to 99% with respect to a distance from the core to the surface of the lithium cobalt oxide particle.

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

8 . The positive electrode active material for a lithium secondary battery of claim 1 , wherein the core part and the shell part each independently comprises lithium distributed with decreasing concentration gradient toward the center of the lithium cobalt oxide particle.

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

10 . The positive electrode active material for a lithium secondary battery of claim 1 , wherein at least one of the core part and the shell part comprises the lithium present with one concentration value in each corresponding region.

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

12 . The positive electrode active material for a lithium secondary battery of claim 1 , comprising a monolith structure with an average particle diameter from 3 to 50 μm.

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

14 . A method of preparing the positive electrode active material for a lithium secondary battery according to claim 1 , the method comprising:
preparing a first lithium cobalt oxide particles by mixing a cobalt raw material and a lithium raw material in amounts satisfying the relation of 0<Li/Co molar ratio<1, and first heating; and mixing a cobalt raw material and a lithium raw material in amounts satisfying the relation of 1≦Li/Co molar ratio with respect to the first lithium cobalt oxide particles, and second heating.

15 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 14 , further comprising an adding process of a 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 during mixing the cobalt raw material and the lithium raw material in preparing the first lithium cobalt oxide particles.

16 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 14 , wherein the step of preparing the first lithium cobalt oxide particles is conducted by mixing the cobalt raw material and the lithium raw material in amounts satisfying the relation of 0.95≦Li/Co molar ratio<1, and heating at from 800° C. to 1,100° C.

17 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 14 , wherein the second heating is conducted at from 800° C. to 1,100° C.

18 . The method of preparing the positive electrode active material for a lithium secondary battery of claim 14 , further comprising an adding process of a 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 mixing the cobalt raw material and the lithium raw material with respect to the first lithium cobalt oxide.

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

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

21 - 24 . (canceled)

Assignees

• Lg Chemical Ltd

Inventors

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

Classifications

• H01M4/1391

  of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• C01G51/00

  Compounds of cobalt · 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

• C01P2004/86

  Thin layer coatings, i.e. the coating thickness being less than 0.1 time the particle radius · CPC title

• C01P2006/40

  Electric properties · CPC title