Cathode active material with whole particle concentration gradient for lithium secondary battery, method for preparing the same, and lithium secondary battery having the same
The present invention relates to an anode active material with whole particle concentration gradient for a lithium secondary battery, a method for preparing same, and a lithium secondary battery having same, and more specifically, to a composite anode active material, a method for manufacturing same, and a lithium secondary battery having same, the composite anode active material having excellent lifetime characteristics and charge/discharge characteristics through the stabilization of crystal structure as the concentration of a metal comprising the anode active material shows concentration gradient in the whole particle, and having thermostability even in high temperatures.
1. A cathode active material for a lithium secondary battery with whole particle concentration gradient comprising:
a core expressed by the following formula 1; and
a surface part expressed by the following formula 2,
Li a1 M1 x M2 y1 M3 z1 M4 w O 2+δ [Formula 1]
Li a2 M1 x M2 y2 M3 z2 M4 w O 2+δ [Formula 2]
wherein
the concentration of the M1 is constant from the core to the surface part;
the concentration of the M2 and the concentration of the M3 have continuous concentration gradient from the core to the surface,
M1 is Ni,
M2 and M3 are selected from the group consisting of Co, Mn and a combination thereof;
M4 is selected from the group consisting of Fe, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, B and a combination thereof; 0<a1≦1.1, 0<a2≦1.1, 0≦x≦1, 0≦y1≦1, 0≦y2≦1, 0≦z1≦1, 0≦z2≦1, 0≦w≦0.1, 0.0≦δ≦0.02, 0<x+y1+z1≦1, 0<x+y2+z2≦1, and y1≦y2, z2≦z1;
the concentration of a metal making up the cathode active material for a lithium secondary battery shows continuous concentration gradient in the entire region, from the particle core to the surface part; and
the center part of the particle is within the radius 0.2 μm from the middle of the active material particle.
2. The cathode active material according to claim 1 , wherein the concentration of M2 is increased with continuous concentration gradient from the core to the surface part, and the concentration of M3 is decreased with continuous concentration gradient from the core to the surface part.
3. The cathode active material according to claim 2 , wherein M2 is Mn and the M3 is Co.
4. The cathode active material according to claim 3 , wherein the concentration range of the M1, x is 0.4<x<1.
5. The cathode active material according to claim 4 , wherein the concentration range of the M1 is 0.6≦x≦0.9, 0.2≦|y2−y1|≦0.4, 0.2≦|z2−z1|≦0.4, 0.2≦y2≦0.4 and 0≦z2≦0.1.
6. The cathode active material according to claim 3 , wherein the concentration gradient of the M2 is constant from the particle core to the surface part.
7. The cathode active material according to claim 3 , wherein the concentration gradient of the M3 is constant from the particle core to the surface part.
8. A lithium secondary battery comprising the cathode active material for a lithium secondary battery of claim 1 .