Metal oxide containing multiple dopants and methods of preparing same

Abstract

The present invention relates to metal oxides containing multiple dopants. The metal oxides have the formula: LiM y-x [A] x O z or M y-x [A] x O z , wherein M is a transition metal, 0 < x , y , [ A ] = ∑ i = l n    w i B i wherein B i is an element used to replace the transition metal M and w i is the fractional amount of element B i in the total dopant combination such that ∑ i = l n    w i =1 , n is the total number of dopant elements used and is a positive integer of two or more, wherein the fractional amount w i of dopant element B i is determined by the relationship ∑ i = l n w i E i =the oxidation state of the transition metal M±0.5, E i is the oxidation state of dopant B i in the final product LiM y-x [A] x O z or M y-x [A] x O z the dopant elements B i are cations in the intercalation compound, and the ratio of Li to O in the intercalation compound is not smaller than the ratio of Li to O in the undoped compound LiM y O z or M y O z . The present invention also includes methods of preparing same and specific embodiments of same.

That which is claimed is:  
     
         1 . A doped intercalation compound having the formula:  
       LiM y-x [A] x O z  or M y-x [A] x O z ,  wherein M=a transition metal,              0   <   x   <   y     ,       {   A   }     =       ∑     i   =   l     n            w   i          B   i                             wherein B i  is an element used to replace the transition metal M and w i  is the fractional amount of element B i  in the total dopant combination such that                  ∑     i   =   l     n          w   i       =   1     ,                     and n=total number of dopant elements B i  and is a positive integer of two or more;    wherein the fractional amount w i  of dopant element B i  is determined by the following relation:                  ∑     i   =   1     n            w   i          E   i         =       oxidation                 state                 of                 the                 replaced                 transition                 metal                 ion                 M     ±   0.5       ;                      oxidation state of the replaced transition metal ion M±0.5;    wherein E i  is the oxidation state of dopant B i  in the final product LiM y-x {A} x O z  or M y-x {A} x O z ;    wherein the dopant elements B i  are cations in the intercalation compound and at least two of the dopant elements Bi have a different oxidation state than the oxidation state of M in the LiM y-x {A} x O z  or M y-x {A} x O z ; compound;    wherein the dopant elements B i  include Ti 4+  and Mg 2+ ;    wherein y and z are values that provide a stable metal oxide compound; and    wherein the ratio of Li to O in the doped intercalation compound is not smaller than the ratio of Li to O in the undoped compound LiM y O z  or M y O z .    
     
     
         2 . The intercalation compound of  claim 1 , wherein the dopant elements B i  are any elements other than M having a Pauling's electronegativity not greater than 2.05 or Mo.  
     
     
         3 . The intercalation compound of  claim 1 , wherein the dopant elements B i  include no more than one element from Groups IIIB and IVB.  
     
     
         4 . The intercalation compound of  claim 1 , wherein the fractional amount of Ti 4+  is approximately equal to the fractional amount of Mg 2+ .  
     
     
         5 . The intercalation compound of  claim 1 , wherein the fractional amount of Mg 2+  is no smaller than the fractional amount of Ti 4+ .  
     
     
         6 . A positive electrode for lithium and lithium ions cells comprising an intercalation compound having the formula:  
       LiM y-x [A] x O z  or M y-x [A] x O z ,  wherein M=a transition metal,              0   <   x   <   y     ,       {   A   }     =       ∑     i   =   l     n            w   i          B   i                             wherein w i  is the fractional amount of element B i  in the total dopant combination such that                  ∑     i   =   l     n          w   i       =   1     ,                     and n=total number of dopant elements used and is a positive integer of two or more;    wherein the fractional amount w i  of dopant element B i  is determined by the following relation:                  ∑     i   =   1     n            w   i          E   i         =       oxidation                 state                 of                 the                 replaced                 transition                 metal                 ion                 M     ±   0.5       ;                      oxidation state of the replaced transition metal ion M±0.5;    wherein E i  is the oxidation state of dopant B i  in the final product LiM y-x {A} x O z  or LiM y-x {A} x O z ;    wherein the dopant elements B i  are cations in the intercalation compound and at least two of the dopant elements Bi have a different oxidation state than the oxidation state of M in the LiM y-x {A} x O z  or M y-x {A} x O z ; compound;    wherein the dopant elements B i  include Ti 4+  and Mg 2+ ;    wherein y and z are values that provide a stable metal oxide compound; and    wherein the ratio of Li to O in the doped intercalation compound is not smaller than the ratio of Li to O in the undoped compound LiM y O z  or M y O z .    
     
     
         7 . The positive electrode of  claim 6 , wherein the dopant elements B i  are any elements other than M having a Pauling's electronegativity not greater than 2.05 or Mo.  
     
     
         8 . The positive electrode of  claim 6 , wherein the dopant elements B i  include no more than one element from Groups  111 B and IVB.  
     
     
         9 . The positive electrode of  claim 6 , wherein the fractional amount of Ti 4+  is approximately equal to the fractional amount of Mg 2+ .  
     
     
         10 . The positive electrode of  claim 6 , wherein the fractional amount of Mg 2+  is no smaller than the fractional amount of Ti 4+ .  
     
     
         11 . A method of preparing a doped intercalation compound of the formula LiM y-x {A} x O z  or M y-x {A} x O z , comprising the steps of: 
 mixing source compounds containing M, {A} and optionally Li to provide a stoichiometric relationship between M, {A} and Li corresponding to the formula LiM y-x {A} x O z  or M y-x {A} x O z , wherein M is a transition metal,              0   <   x   <   y     ,       {   A   }     =       ∑     i   =   l     n                       w   i          B   i                             wherein B i  is an element i=1 used to replace the transition metal M and w i  is the fractional amount of element B i  in the total dopant combination, n is the total number of dopant elements and is a positive integer of two or more, the fractional amount w i  of dopant element B i  is determined by the relationship:                  ∑     i   =   l     n                       w   i          E   i         =       oxidation                 state                 of                 the                 replaced                 transition                 metal                 ion                 M     ±   0.5       ,                     E i  is the oxidation state of dopant B i  in the final product LiM y-x {A} x O z  or LiM y-x {A} x O z , the dopant elements B i  are selected to be cations in the intercalation compound, at least two of the dopant elements B i  have a different oxidation state than the oxidation state of M in the LiM y-x {A} x O z  or M y-x {A} x O z  compound, the dopant elements B i  include Ti 4+  and Mg 2+ , y and z are values that provide a stable metal oxide compound; and the ratio of Li to O in the doped intercalation compound is not smaller than the ratio of Li to O in the undoped compound LiM y O z  or M y O z ;    firing the mixture at a temperature between 500° C. and 1000° C. in the presence of oxygen to produce the doped intercalation compound; and    cooling the doped intercalation compound.    
     
     
         12 . The method of  claim 11 , wherein the step of mixing source compounds comprising mixing source compounds containing a transition metal M selected from Co, Ni, Mn, Fe, V and Mo.  
     
     
         13 . The method of  claim 11 , wherein the step of mixing source compounds comprising mixing source compounds containing dopant elements Bi other than M having a Pauling's electronegativity not greater than 2.05 or Mo.  
     
     
         14 . The method of  claim 11 , wherein the step of mixing source compounds comprising mixing source compounds containing dopant elements Bi wherein the dopant elements B i  include no more than one element from Groups  111 B and IVB.  
     
     
         15 . The method of  claim 11 , wherein the step of mixing source compounds comprising mixing source compounds containing Ni or Co as the transition metal M to form an intercalation compound having the formula LiMY-X{A} x O z .  
     
     
         16 . The method of  claim 15 , wherein the step of mixing source compounds comprising mixing source compounds containing Ni as the transition metal M.  
     
     
         17 . The method of  claim 11 , wherein the step of mixing source compounds comprises preparing a solution comprising M and {A} from source compounds comprising M and {A}, precipitating the M and {A} out of solution to produce an intimately mixed hydroxide, and blending the mixed hydroxide with a lithium source compound.