Positive active material for rechargeable lithium ion battery, preparing method of the same, and rechargeable lithium ion battery comprising the same

Abstract

The present disclosure relates to a positive electrode active material for rechargeable lithium ion batteries and a method of preparing the positive electrode active material, in which a compound including sulfur is used as an additive in a wet treatment process to remove residual lithium impurities (LiOH, Li2CO3) present on a surface of the positive electrode active material, such that the residual lithium impurities are effectively removed without loss of capacity while a Li-S compound coating layer is formed on the surface thereof, thereby reducing resistance and leakage current.

What is claimed is: 
     
         1 . A positive electrode active material for rechargeable lithium ion batteries comprising:
 a lithium metal oxide active material; and   a coating layer on a surface of the lithium metal oxide active material,   wherein the coating layer comprises a sulfur compound.   
     
     
         2 . The positive electrode active material for rechargeable lithium ion batteries of  claim 1 , wherein the sulfur compound comprises at least one selected from the group consisting of Li 2 S, Li 2 SO 4 , and Li 2 S n O x , wherein n is 1≤n≤8. 
     
     
         3 . The positive electrode active material for rechargeable lithium ion batteries of  claim 1 , wherein the sulfur compound is included in the coating layer in an amount ranging from 0.5 percent by weight (wt %) to 5.0 wt % with respect to the total weight of the positive electrode active material. 
     
     
         4 . The positive electrode active material for rechargeable lithium ion batteries of  claim 1 , wherein the lithium metal oxide active material is represented by the following Chemical Formula 1:
   Li a Ni b Co c Mn d M e O 2    Chemical Formula 1
   wherein, M is a metal of Al, Zr, B or a combination thereof, 0.98<a<1.2, 0.6≤b≤0.9, 0.05≤c≤0.2, 0.01≤d≤0.2, 0.01≤e<0.05, and b+c+d+e=1.   
     
     
         5 . A method of preparing a positive electrode active material for rechargeable lithium ion batteries, the method comprising:
 primary heat-treating a precursor material and a lithium material to obtain a lithium metal oxide;   dissolving a sulfur material in water to prepare a washing solution;   immersing the lithium metal oxide in the washing solution to wash the lithium metal oxide; and   secondary heat-treating the washed lithium metal oxide.   
     
     
         6 . The method of  claim 5 , wherein the secondary heat-treating is performed at a temperature ranging from 130° C. to less than 550° C. 
     
     
         7 . The method of  claim 5 , wherein a total amount of LiOH and Li 2 CO 3  which are a residual lithium of the lithium metal oxide obtained by the primary heat-treating of the precursor material and the lithium material is substantially equal to or more than 6,000 ppm. 
     
     
         8 . The method of  claim 5 , wherein the sulfur material is a compound of M z S x O y , wherein x ranges from 1 to 8, y ranges from 1 to 8, M is Na or K, and z ranges from 0 to 3. 
     
     
         9 . The method of  claim 6 , wherein the sulfur material is selected from the group consisting of Na 2 SO 3 , Na 2 SO 4 , Na 2 SO 5 , Na 2 SO 8 , Na 2 S 2 O 3 , Na 2 S 2 O 4 , Na 2 S 2 O 5 , Na 2 S 2 O 8 , K 2 SO 3 , K 2 SO 4 , K 2 SO 5 , K 2 SO 8 , K 2 S 2 O 3 , K 2 S 2 O 4 , K 2 S 2 O 5 , and K 2 S 2 O 8 .