Positive electrode active material and lithium secondary battery comprising the same

1. A positive electrode active material, comprising:

a lithium composite oxide comprising primary particles and secondary particles formed by agglomerating the primary particles; and

at least one lithium alloy oxide existing at least at a part of a) the interface between the primary particles and b) the surface of the secondary particle;

wherein the lithium alloy oxide has a peak in which at least one of peaks specific to the lithium tungsten oxide represented by Formula 2 below is shifted toward a low angle in X-ray diffraction:

Li d W e O f   [Formula 2]

(wherein, 0<d≤6, 0<e≤6, 0<f≤10).

2. The positive electrode active material of claim 1 , wherein the primary particles forming the lithium composite oxide are represented by Formula 6 below:

Li w Ni 1−(x+y+z) Co x M3 y M4 z O 2   [Formula 6]

(wherein, M3 is at least one selected from Mn and Al, M4 is at least one selected from Ti, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ta, Fe, Cr, Sn, Hf, Ce, W, Nd and Gd, 0.5≤w≤1.5, 0≤x≤0.50, 0≤y≤0.20, and 0≤z≤0.20).

3. The positive electrode active material of claim 1 , wherein the lithium alloy oxide has a peak in which at least one of (110), (200) and (220) peaks specific to the lithium tungsten oxide is shifted toward a low angle in X-ray diffraction.

4. The positive electrode active material of claim 1 , wherein the lithium alloy oxide exhibits a concentration gradient which decreases from the surface to the center of the secondary particle.

5. The positive electrode active material of claim 1 , wherein the lithium allow oxide has a lattice structure that is doped with at least one dopant in the lithium tungsten oxide.

6. The positive electrode active material of claim 1 , wherein the lithium allow oxide has a lattice structure in which tungsten in the lattice structure formed by the lithium tungsten oxide is partially substituted with at least one dopant.

7. The positive electrode active material of claim 1 , wherein the lithium alloy oxide represented by Formula 1-1 below:

Li a (W 1−y M1 y ) b O c   [Formula 1-1]

(wherein, M1 includes at least one selected from Ti, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ta, Fe, Cr, Sn, Hf, Ce, Nd and Gd, 0<a≤6, 0<b≤6, 0<c≤10, and 0<y≤0.50).

8. The positive electrode active material of claim 1 , further comprising:

at least one alloy oxide represented by Formula 3 below and existing at least a part of a) the interface between the primary particles and b) the surface of the secondary particle:

Li g M2 h O i   [Formula 3]

(wherein, M2 is at least one selected from Ti, Zr, Mg, V, B, Mo, Zn, Nb, Ba, Ta, Fe, Cr, Sn, Hf, Ce, Nd and Gd, 0≤g≤6, 0<h≤6, and 0<i≤10).

9. The positive electrode active material of claim 8 , wherein the alloy oxide exhibits a concentration gradient which decreases from the surface to the center of the secondary particle.

10. A lithium secondary battery comprising a positive electrode including the positive electrode active material according to claim 1 .