Positive active material

Abstract

A positive active material for a rechargeable lithium battery includes a core including a compound represented by Chemical Formula 1 and a structure-stabilizing compound on a surface of the core. The structure-stabilizing compound includes an Al compound or a Co compound. Chemical Formula 1 is Li a Ni x Co y Me z M 1 k O 2−p F p where 0.9≤a≤1.1, 0.7≤x≤0.93, 0<y≤0.3, 0<z≤0.3, 0≤k≤0.005, x+y+z+k=1, 0≤p≤0.005, Me is Mn or Al, and Ml is Mg, Ba, B, La, Y, Ti, Zr, Mn, Si, V, P, Mo, W, or a combination thereof.

1 .- 8 . (canceled) 
     
     
         9 . A positive active material formed by a process comprising:
 mixing a core including a compound represented by Chemical Formula 1 and Co(OH) 2  in a water solvent, and   heat-treating the mixture at about 500° C. to about 800° C. for about 5 to about 20 hours, thereby preparing the positive active material,
   Li a Ni x Co y Me z M 1   k O 2−p F p    [Chemical Formula 1]
 
   wherein, 0.9≤a≤1.1, 0.7≤x≤0.93, 0<y≤0.3, 0≤z≤0.3, 0≤k≤0.005, x+y+z+k=1, 0 p≤0.005,   Me is Mn or Al, and   M 1  is Mg, Ba, B, La, Y, Ti, Zr, Mn, Si, V, P, Mo, W, or a combination thereof.   
     
     
         10 . The positive active material as claimed in  claim 9 , wherein mixing the core including the compound represented by Chemical Formula 1 and Co(OH) 2  includes mixing Co(OH) 2  in an amount of about 1.5 wt % to about 3 wt % based on 100 wt % of the core. 
     
     
         11 . The positive active material as claimed in  claim 9 , wherein heat-treating the mixture is at 700° C. under an oxygen atmosphere for 10 hours. 
     
     
         12 . The positive active material as claimed in  claim 9 , wherein the positive active material prepared by the process includes the core and Co 3 O 4  and Li a CoO 2  on the surface of the core.