Synthesis of cathode active materials

Abstract

The present invention relates to a method for preparing an electroactive metal polyanion or a mixed metal polyanion comprising forming a slurry comprising a polymeric material, a solvent, a polyanion source or alkali metal polyanion source and at least one metal ion source; heating said slurry at a temperature and for a time sufficient to remove the solvent and form an essentially dried mixture; and heating said mixture at a temperature and for a time sufficient to produce an electroactive metal polyanion or electroactive mixed metal polyanion. The electrochemically active materials so produced are useful in making electrodes and batteries.

1 . An electrode active material of the formula  
         A a MI b MII c (XY 4 ) d Z e    wherein:    (i) A comprises at least one alkali metal selected from the group consisting of Li, Na, K, and mixtures thereof and 0<a=6:    (ii) MI comprises a metal ion of a metal selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Si, Sn, Pb and mixtures thereof and 0<b=4;    (iii) MII comprises a metal ion of a metal selected from the group consisting of Be, Mg, Ca, Sr, Ba, Zn, Cd, Ge, Sc, Y, B, Al, Ga and mixtures thereof and 0=c=4;    (iv) XY 4  is selected from the group consisting of X′[O 4-x ,Y′ x ], X′[O 4-y Y′ 2y ], X″S 4 , [X z ′″,X′ 1-z ]O 4  and mixtures thereof wherein: 
 (a) X′ and X′″ are each independently selected from the group consisting of P, As, Sb, Si, Ge, S and mixtures thereof;  
 (b) X″ is selected from the group consisting of P, As, Sb, Si, Ge, V and mixtures thereof;  
 (c) Y′ is selected from the group consisting of a halogen, and mixtures thereof; and  
 (d) 0=x=3, 0<y<2, and 0<z<1; and  
   (i) Z is selected from the group consisting of OH, a halogen and mixtures thereof, and 0<d=6;    wherein A, M, X, Y, Z, a, b, x, y, z, c and d are selected so as to maintain electroneutrality of the material made by a process comprising the steps of:    forming a mixture comprising a solvent having a boiling point, a polyanion source, a source of at least one metal ion, an alkali metal and a polymeric material wherein the polymeric material forms a solution with the solvent without substantial phase separation;    heating the mixture at a temperature greater than the boiling point of the solvent for a period of time sufficient to remove substantially all of the solvent to produce an essentially dried mixture;    heating the dried mixture at a temperature and for a period of time sufficient to produce the electrode active material.    
     
     
         2 . The electrode active material according to  claim 1  wherein the mixture or dried mixture produced in the process further comprises a carbon source.  
     
     
         3 . The electrode active material according to  claim 1  wherein during the heating steps the polymeric material decomposes to form an electron conductive network throughout the electrode active material.  
     
     
         4 . The electrode active material according to  claim 1  wherein the solvent used in the process is selected from the group consisting of water, deionized water, PC, EC, DMF, DME, THF, BL, NMP, DMSO and mixtures thereof.  
     
     
         5 . The electrode active material according to  claim 4 , wherein the polyanion source used in the process is polyanion-containing compound selected from the group consisting of a PO 4 -containing compound, a SiO 4  containing compound, a GeO 4 -containing compound, a VO 4 -containing compound, an AsO 4 -containing compound, a SbO 4 -containing compound, and a SO 4 -containing compound.  
     
     
         6 . The electrode active material according to  claim 5  wherein the polyanion-containing compound used in the process is a PO 4 -containing compound.  
     
     
         7 . The electrode active material according to  claim 6  wherein the PO 4 -containing compound used in the process is selected from the group consisting of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, lithium dihydrogen phosphate and mixtures thereof.  
     
     
         8 . The electrode active material according to  claim 1  wherein the source of at least one metal ion used in the process is a compound of a metal selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Si, Sn, Pb and mixtures thereof.  
     
     
         9 . The electrode active material according to  claim 1  wherein the electrode active material produced is lithium vanadium phosphate.  
     
     
         10 . The electrode active material according to  claim 1  wherein the material produced is of the formula LiFe 1-x Mg x PO 4  wherein x is from about 0.01 to about 0.1.  
     
     
         11 . A cathode comprising the electrode active material of  claim 1 .  
     
     
         12 . A battery comprising a cathode according to  claim 11.