Method of preparing material for lithium secondary battery of high performance

Abstract

Provided is a method for preparing a lithium mixed transition metal oxide, comprising subjecting Li 2 CO 3 and a mixed transition metal precursor to a solid-state reaction under an oxygen-deficient atmosphere with an oxygen concentration of 10 to 50% to thereby prepare a powdered lithium mixed transition metal oxide having a composition represented by Formula I of Li x M y O 2 wherein M, x and y are as defined in the specification. Therefore, since the high-Ni lithium mixed transition metal oxide having a given composition can be prepared by a simple solid-state reaction in air, using a raw material that is cheap and easy to handle, the present invention enables industrial-scale production of the lithium mixed transition metal oxide with significantly decreased production costs and high production efficiency. Further, the thus-produced lithium mixed transition metal oxide is substantially free of impurities, and therefore can exert a high capacity and excellent cycle stability, in conjunction with significantly improved storage stability and high-temperature stability.

1 . A method for preparing a lithium mixed transition metal oxide, comprising subjecting Li 2 CO 3  and a mixed transition metal precursor to a solid-state reaction under an oxygen-deficient atmosphere with an oxygen concentration of 10 to 50% by volume to thereby prepare a powdered lithium mixed transition metal oxide having a composition represented by Formula I below:  
         Li x M y O 2   (I)  wherein:    M=M′ 1−k A k , wherein M′ is Ni 1−a−b (Ni 1/2 Mn 1/2 ) a Co b , 0.65≦a+b≦0.85 and 0.1≦b≦0.4;    A is a dopant;    0≦k≦0.05; and    x+y≈2 and 0.95≦x≦1.05.    
     
     
         2 . The method according to  claim 1 , wherein the oxygen concentration is 10% to 30% by volume.  
     
     
         3 . The method according to  claim 2 , wherein the atmosphere is an air atmosphere.  
     
     
         4 . The method according to  claim 1 , wherein the mixed transition metal precursor is at least one selected from the group consisting of M(OH) 2  and MOOH wherein M is as defined in Formula I.  
     
     
         5 . The method according to  claim 4 , wherein the mixed transition metal precursor is MOOH, and is prepared by an ammonia-free process.  
     
     
         6 . The method according to  claim 1 , wherein the mixed transition metal precursor has a tap density of 1.1 to 1.6 g/cm 3 .  
     
     
         7 . The method according to  claim 1 , wherein a mixing ratio of Li 2 CO 3  and the mixed transition metal precursor is 0.95 to 1.04:1 wherein the ratio of Li 2 CO 3 :mixed transition metal precursor is a w/w ratio.  
     
     
         8 . The method according to  claim 1 , wherein the solid-state reaction includes a sintering process at 600 to 1,100° C. for 3 to 20 hours.  
     
     
         9 . The method according to  claim 8 , wherein an amount of air exceeding 2 m 3 /kg LiMO 2  during the sintering process is supplied to a reaction vessel equipped with a heat exchanger for pre-warming of the air.  
     
     
         10 . The method according to  claim 1 , wherein the lithium mixed transition metal oxide is prepared by a large-scale process of 5 kg or more under a high rate of air circulation of at least 2 m 3  of air by volume at room temperature per 1 kg of the final lithium mixed transition metal oxide.  
     
     
         11 . The method according to  claim 10 , wherein for the high rate of air circulation, the air is pumped into or out of the reaction vessel.  
     
     
         12 . The method according to  claim 11 , wherein at least 10 m 3  of air per 1 kg of the final lithium mixed transition metal oxide is pumped into or out of the reaction vessel.  
     
     
         13 . The method according to  claim 9 , wherein the heat exchanger pre-warms in-flowing air before the in-flowing air enters the reaction vessel, while cooling the out-flowing air.  
     
     
         14 . A lithium mixed transition metal oxide prepared by the method of  claim 1 .  
     
     
         15 . A lithium secondary battery comprising the lithium mixed transition metal oxide of  claim 14  as a cathode active material.