Cathode active material coated with flourine compound for lithium secondary batteries and method for preparing the same

1. A cathode active material for lithium secondary batteries wherein a surface of the cathode active material is coated with a fluorine compound powder, the coated surface of the cathode active material having a powdery form structure, wherein the fluorine compound is at least one compound selected from the group consisting of CsF, KF, NaF, RbF, TiF, AgF, AgF 2 , BaF 2 , CaF 2 , CuF 2 , CdF 2 , FeF 2 , HgF 2 , Hg 2 F 2 , MnF 2 , NiF 2 , PbF 2 , SnF 2 , SrF 2 , XeF 2 , ZnF 2 , AlF 3 , BF 3 , BiF 3 , CeF 3 , CrF 3 , DyF 3 , EuF 3 , GaF 3 , GdF 3 , FeF 3 , HoF 3 , InF 3 , LaF 3 , LuF 3 , MnF 3 , NdF 3 , VOF 3 , PrF 3 , SbF 3 , ScF 3 , SmF 3 , TbF 3 , TiF 3 , TmF 3 , YF 3 , YbF 3 , TlF 3 , CeF 4 , GeF 4 , HfF 4 , SiF 4 , SnF 4 , TiF 4 , VF 4 , ZrF 4 , NbF 5 , SbF 5 , TaF 5 , BiF 5 , MoF 5 , ReF 5 , SF 5 , WF 5 , MoF 6 , ReF 6 , SF 6 , and WF 6 .

2. The cathode active material of claim 1 , wherein:

the cathode active material coated has a hexagonal rock-salt structure and is represented by formula:

Li[Co 1−x M x ]O 2

wherein:

0≦x≦0.1; and

M is at least one metal selected from the group consisting of Mg, Al, Ni, Mn, Zn, Fe, Cr, Ga, Mo and W.

3. The cathode active material of claim 1 , wherein the cathode active material coated has a hexagonal rock-salt structure and is represented by formula:

Li 1+a [Ni 1−x M x ]O 2−b F b or Li 1+a [Ni 1−x M x ]O 2−b S b

wherein:

0.01≦a≦0.2, 0≦b≦0.1, 0.01≦x≦0.5, and

M is at least one metal selected from the group consisting of Mg, Al, Ni, Mn, Zn, Fe, Cr, Ga, Mo and W.

4. The cathode active material of claim 1 , wherein the cathode active material coated has a hexagonal rock-salt structure and has formula:

Li 1+a [Ni 1−x−y Co x Mn y ]O 2−b F b or Li 1+a [Ni 1−x−y Co x Mn y ]O 2−b S b

wherein:

0.01≦a≦0.2, 0≦b≦0.1, 0.05≦x≦0.4, 0.05≦y≦0.35, and 0.1≦x+y≦0.

5. The cathode active material of claim 1 , wherein the cathode active material coated has a hexagonal rock-salt structure and is represented by formula:

Li[Li a (Ni x Co 1−2x Mn x ) 1−a ]O 2−b F b or Li[Li a (Ni x Co 1−2x Mn x ) 1−a ]O 2 S b

wherein:

0.01≦a≦0.2, 0.05≦x≦0.5, 0≦b≦0.1.

6. The cathode active material of claim 1 , wherein the cathode active material coated has a hexagonal rock-salt structure and is represented by formula:

Li[Li a (Ni x Co 1−2x Mn x-0.5y M y ) 1−a ]O 2−b F b or Li[Li a (Ni x Co 1−2x Mn x-0.5y M y ) 1−a ]O 2−b S b

wherein:

M is at least one metal selected from the group consisting of Mg, Ca, Cu and Zn;

0.01≦a≦0.2, 0≦x≦0.5, 0.01≦y≦0.1, and 0≦b≦0.1.

7. The cathode active material of claim 1 , wherein the cathode active material coated has a hexagonal rock-salt structure and is represented by formula:

Li[Li a (Ni 1/3 Co (1/3−2x) Mn (1/3+x) M x ) 1−a ]O 2−b F b or Li[Li a (Ni 1/3 Co (1/3−2x) Mn (1/3+x) M x ) 1−a ]O 2−b S b

wherein:

M is at least one metal selected from the group consisting of Mg, Ca, Cu and Zn;

0.01≦a≦0.2, 0≦x≦0.5, 0.01≦y≦0.1, and 0≦b≦0.1.

8. The cathode active material of claim 1 , wherein the cathode active material coated has a hexagonal rock-salt structure and is represented by formula:

Li[Li a (Ni x Co 1−x−y )Mn x M y ) 1−a ]O 2−b F b or Li[Li a (Ni x Co 1−x−y )Mn x M y ) 1−a ]O 2−b S b

wherein:

M is at least one metal selected from the group consisting of B, Al M, Fe and Cr;

0.01≦a≦0.2, 0.05≦x≦0.5, 0.01≦y≦0.1, and 0≦b≦0.1.

9. The cathode active material of claim 1 , wherein the cathode active material has a hexagonal layered rock-salt structure and is represented by formula is:

Li[Li a (Ni x Co 1−2x−y Mn x-0.5z M y M′ z ) 1−a ]O 2−b F b or Li[Li a (Ni x Co 1−2x−y Mn x-0.5z M y M′ z ) 1−a ]O 2−b S b

wherein:

M is at least one metal selected from the group consisting of B, Al M, Fe, and Cr;

M′ is Mg or Ca;

0.01≦a≦0.2, 0≦x≦0.5, 0.01≦y≦0.1, and 0.01≦b≦0.1.

10. The cathode active material of claim 1 , wherein the cathode active material has an olivine structure and is represented by formula: is

LiM x Fe 1−x PO 4

wherein:

M is at least one metal selected from the group consisting of Co, Ni and Mn, and 0≦x≦1.

11. The cathode active material of claim 1 , wherein the cathode active material is a spinel having a cubic structure and is represented by formula:

Li 1+a [Mn 2−x M x )O 4−b F b or Li 1+a [Mn 2−x M x ]O 4−b S b

wherein:

0.01≦a≦0.15, 0≦b≦0.1, 0≦x≦0.1; and

M is at least one metal selected from the group consisting of Co, Ni, Cr, Mg, Al M, Zn, Mo and W.

12. The cathode active material of claim 1 , wherein the cathode active material is a spinel having a cubic structure and is represented by formula:

Li 1+a (Ni 0.5 Mn 2−x M x ]O 4−b F b or Li 1+a [Ni 0.5 Mn 2−x M x ]O 4−b S b

wherein:

0.01≦a≦0.15, 0≦b≦0.1, 0≦x≦0.1; and

M is at least one metal selected from the group consisting of Co, Ni, Cr, Mg, Al M, Zn, Mo and W.