Positive electrode materials for lithium ion batteries having a high specific discharge capacity and processes for the synthesis of these materials

Abstract

Positive electrode active materials are described that have a very high specific discharge capacity upon cycling at room temperature and at a moderate discharge rate. Some materials of interest have the formula Li 1+x Ni 60 Mn β Co γ O 2 , where x ranges from about 0.05 to about 0.25, α ranges from about 0.1 to about 0.4, β range's from about 0.4 to about 0.65, and γ ranges from about 0.05 to about 0.3. The materials can be coated with a metal fluoride to improve the performance of the materials especially upon cycling. Also, the coated materials can exhibit a very significant decrease in the irreversible capacity lose upon the first charge and discharge of the cell. Methods for producing these materials include, for example, a co-precipitation approach involving metal hydroxides and sol-gel approaches.

What is claimed is: 
     
         1 . A method for the synthesis of a layered lithium metal oxide composition, the method comprising,
 precipitating a mixed metal hydroxide composition from a solution comprising +2 metal cations wherein the hydroxide composition has a selected composition;   heating the hydroxide composition to form a metal oxide composition;   homogenizing the metal oxide composition to form a powder; and   heating the metal oxide composition powder to form a crystalline layered lithium metal oxide composition.   
     
     
         2 . The method of  claim 1  wherein the solution comprises acetate anions, sulfate anions, nitrate anions or combinations thereof. 
     
     
         3 . The method of  claim 1  wherein the solution comprising +2 metal cations was mixed with a hydroxide solution that comprises lithium cation to form the mixed metal hydroxide composition. 
     
     
         4 . The method of  claim 1  wherein the solution further comprises lithium cations. 
     
     
         5 . The method of  claim 1  wherein the precipitating step is carried out in an oxygen free atmosphere. 
     
     
         6 . The method of  claim 1  wherein the lithium metal oxide composition can be approximately represented by a formula Li 1+x Ni α Mn β Co γ M δ O 2−z F z , where x ranges from about 0.05 to about 0.25, a ranges from about 0.1 to about 0.4, β ranges from about 0.4 to about 0.65, γ ranges from about 0.05 to about 0.3, δ ranges from about 0 to about 0.1 and z ranges from about 0 to about 0.1, and where M is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb or combinations thereof. 
     
     
         7 . The method of  claim 1  wherein the lithium metal oxide composition can be approximately represented by a formula of xLiMO 2 .(1−x)Li 2 M′O 3 , wherein M′ comprises Mn and M comprises Mn, Co and Ni. 
     
     
         8 . The method of  claim 1  further comprising drying the mixed metal hydroxide composition while heating in an oxygen free atmosphere for at least 5 hours before heating the hydroxide composition to form the corresponding metal oxide composition. 
     
     
         9 . The method of  claim 1  further comprising mixing a lithium source in powder form with the metal hydroxide composition to form a mixture before heating the hydroxide composition mixture to form the corresponding metal oxide composition. 
     
     
         10 . The method of  claim 9  wherein the lithium source is lithium hydroxide powder. 
     
     
         11 . The method of  claim 1  wherein the solution further comprises lithium cations and the method further comprising adding a lithium source composition to the metal hydroxide composition to form a mixture before heating the hydroxide composition mixture to form the corresponding metal oxide composition. 
     
     
         12 . The method of  claim 1  further comprising applying a stabilization coating composition to the lithium metal oxide composition to form a positive electrode active material. 
     
     
         13 . The method of  claim 12  wherein the lithium metal oxide composition is homogenized in a coating solution that comprises the cation of the coating composition before the addition of a solution comprising the counter anion of the coating composition to deposit the coating composition onto the lithium metal oxide composition through precipitation. 
     
     
         14 . The method of  claim 12  wherein the positive electrode active material comprises from about 0.5 mole percent to about 4 mole percent metal fluoride as the stabilization coating. 
     
     
         15 . The method of  claim 12  wherein the stabilization coating comprises AlF 3 . 
     
     
         16 . The method of  claim 12  wherein the stabilization coating comprises Al 2 O 3 . 
     
     
         17 . The method of  claim 12  wherein the positive electrode active material having a discharge capacity at a 10th discharge cycle of at least 250 mAh/g at room temperature at a discharge rate of C/3 when discharged from 4.6 volts to 2.0 volts after the material is activated in the first cycle through a charge to 4.6V at a rate of C/10. 
     
     
         18 . The method of  claim 12  wherein the positive electrode active material has a first cycle irreversible capacity loss at a discharge rate of C/10 of no more than about ⅔ of the first cycle irreversible capacity loss of the lithium metal oxide composition, which corresponds to the positive electrode active material without the stabilization coating. 
     
     
         19 . The method of  claim 12  wherein positive electrode active material has a discharge capacity at a 10th discharge cycle between about 260 and about 275 mAh/g at room temperature at a discharge rate of C/3 when discharged from 4.6 volts to about 2.0 volts. 
     
     
         20 . The method of  claim 12  wherein the positive electrode active material has a discharge capacity at the 20th cycle that is at least about 98% of the 5th cycle discharge capacity when discharged at room temperature at a discharge rate of C/3.