Positive active material for rechargeable lithium battery, method of preparing same, and rechargeable lithium battery including same

Patent metadata

Field	Value
Publication number	US-9722241-B2
Application number	US-201514682022-A
Country	US
Kind code	B2
Filing date	Apr 8, 2015
Priority date	Jun 17, 2014
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

A positive active material for a rechargeable lithium battery includes a core including an overlithiated oxide represented by Chemical Formula 1, a first coating layer on the core and including a compound having a spinel structure, and a second coating layer on the first coating layer and including a compound represented by Chemical Formula 2. The compound having a spinel structure shows a peak between about 2.6 V and about 2.7 V in a graph of differential capacity dQ/dV vs. voltage, where the voltage is between about 4.7 V and about 2.5 V. In Chemical Formula 1, 0<x<1, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1. In Chemical Formula 2, 0≦d<1 and 0<e≦1.

xLi 2 MnO 3 .(1−x)LiNi a Co b Mn c O 2 ,  Chemical Formula 1

Li d Ti e O 2 .  Chemical Formula 2

First claim

What is claimed is:

1. A positive active material for a rechargeable lithium battery comprising:
a core comprising an overlithiated oxide represented by Chemical Formula 1;
a first coating layer on the core comprising a compound having a spinel structure; and
a second coating layer on the first coating layer comprising a compound represented by Chemical Formula 2,
wherein the compound having a spinel structure has a peak between about 2.6 V and about 2.7 V in a graph of differential capacity dQ/dV versus voltage, the voltage of the graph being between about 4.7 V and about 2.5 V:
xLi 2 MnO 3 .(1−x)LiNi a Co b Mn c O 2 ,   Chemical Formula 1

wherein 0<x<1, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1,
Li d Ti e O 2 ,   Chemical Formula 2

wherein 0≦d<1 and 0<e≦1.

2. The positive active material of claim 1 , wherein the compound having a spinel structure is a compound represented by Chemical Formula 3:
Li f M g O h ,   Chemical Formula 3

wherein M is Mn, Co, Ni, or a combination thereof, 0<f<1, 1.9<g<2.1, and 3.9<h<4.1.

3. The positive active material of claim 1 , wherein the second coating layer comprises about 0.1 parts by mole to about 5 parts by mole of titanium (Ti) based on 100 parts by mole of the core.

4. The positive active material of claim 1 , wherein the second coating layer is about 10 nm to about 50 nm thick.

5. The positive active material of claim 1 , wherein the first and second coating layers have a total thickness of about 15 nm to about 60 nm.

6. The positive active material of claim 1 , wherein the positive active material has an average particle diameter (D50) of about 100 nm to about 500 nm.

7. A rechargeable lithium battery comprising:
a positive electrode including the positive active material of claim 1 ;
a negative electrode; and
an electrolyte.

8. A method of preparing the positive active material for a rechargeable lithium battery, the method comprising:
co-precipitating a nickel (Ni) source, a cobalt (Co) source, and a manganese (Mn) source with ammonium hydroxide (NH 4 OH) or sodium hydroxide (NaOH) to obtain a precipitate;
mixing the precipitate with a lithium source to obtain a first mixture;
treating the first mixture with a primary heat treatment to obtain an overlithiated oxide represented by Chemical Formula 1;
mixing an alcohol and a titanium (Ti) source to obtain a second mixture;
mixing the second mixture and the overlithiated oxide to obtain a third mixture; and
treating the third mixture with a secondary heat treatment to obtain the overlithiated oxide coated with a compound having a spinel structure and a compound represented by Chemical Formula 2:
xLi 2 MnO 3 .(1−x)LiNi a Co b Mn c O 2 ,   Chemical Formula 1

wherein 0<x<1, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1,
Li d Ti e O 2 ,   Chemical Formula 2

wherein 0≦d<1 and 0<e≦1.

9. The method of claim 8 , wherein the titanium (Ti) source comprises titanium isopropoxide, a TiO 2 powder, or a combination thereof.

10. The method of claim 9 , wherein the titanium (Ti) source is the TiO 2 powder having an average particle diameter (D50) of about 10 nm to about 50 nm.

11. The method of claim 8 , wherein the titanium (Ti) source is in an amount of about 0.1 parts by mole to about 5 parts by mole based on 100 parts by mole of the overlithiated oxide.

12. The method of claim 8 , wherein the primary heat treatment is performed at about 600° C. to about 1000° C.

13. The method of claim 8 , wherein the secondary heat treatment is performed at about 300° C. to about 800° C.

Assignees

• Samsung Sdi Co Ltd

Inventors

• Kim Ji-Hyun
• Kim Chang-Wook
• Cho Sang-Woo
• You Yong-Chan

Classifications

• C01P2004/64

  Nanometer sized, i.e. from 1-100 nanometer · CPC title

• H01M4/0471

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

• C01G45/1257

  containing lithium, e.g. Li2MnO3 or Li2(MxMn1-x)O3 · CPC title

• H01M4/131

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

• C01P2004/03

  obtained by SEM · CPC title