Additive for cathode, method for preparing the same, cathode including the same, and lithium secondary battery including the same

1. A cathode additive for a lithium secondary battery, comprising:

a composite represented by the following Chemical Formula 1:

(1- y - z )(Li 6 Co 1-x M x O 4 )- y (LiCo 1-x M x O 2 )- z (Li 2 O),  [Chemical Formula 1]

wherein M comprises one or more elements selected from the group consisting of P, B, F, Ni, W, Ti, Zr, Mg and Al,

0≤ x< 1.0,

wherein y and z are molar ratios of LiCo 1-x M x O 2 and Li 2 O contained in the composite of Chemical Formula 1, 0<y≤0.10, and 0≤z≤0.20,

wherein the composite comprises the Li 6 Co 1-x M x O 4 , the LiCo 1-x M x O 2 and the physically mixed and connected to form a single particulate or a complex.

2. The cathode additive for a lithium secondary battery of claim 1 ,

wherein the composite of Chemical Formula 1 in the form of a single particulate or a complex has an additional peak at 2θ of 18.98°±0.2° or 45.27°±0.2° in XRD (X-ray diffraction) analysis by Cu Kα X-ray (X-rα), and

an intensity of the additional peak is 2 to 25% based on an intensity of the peak at 2θ of 23.5°±0.2°.

3. The cathode additive for a lithium secondary battery of claim 1 ,

wherein the cathode additive comprises the LiCo 1-x M x O 2 in an amount of greater than 0 wt % and 0.1 wt % or less, and the Li 2 O in an amount of 0 to 0.7 wt %, based on a total amount of the cathode additive as 100 wt %.

4. A method for preparing a cathode additive of a lithium secondary battery of claim 1 , comprising a step of:

forming a composite represented by the Chemical formula 1 by mixing and calcining a mixture comprising a cobalt precursor and a lithium precursor comprising Li 2 O under an inert atmosphere at a temperature of 500° C. or greater and less than 700° C.

5. The method for preparing the cathode additive of claim 4 ,

wherein the mixture further comprises an M-containing precursor.

6. The method for preparing the cathode additive of claim 5 ,

wherein the cobalt precursor comprises one or more selected from the group consisting of cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, cobalt sulfate, cobalt nitrate, cobalt acetate, cobalt carbonate, cobalt oxalate, cobalt citrate, cobalt halide, cobalt phosphate, and hydrate thereof, and

the M precursor comprises at least one selected from the group consisting of an oxide, hydroxide, oxyhydroxide, sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, phosphate and hydrate of the element M.

7. A cathode mix comprising the cathode additive of claim 1 ; and a cathode active material.

8. The cathode mix of claim 7 ,

wherein a weight ratio of the cathode additive:the cathode active material is 1:99 to 35:65.

9. The cathode mix of claim 7 ,

wherein the cathode active material comprises one or more selected from the group consisting of composite oxides of a metal of cobalt, manganese, and nickel; and lithium.

10. A lithium secondary battery comprising: a cathode comprising a cathode mix of claim 7 ; an electrolyte; and an anode.