Patent ID: 6913855

Claim:
A method of making an active material for a rechargeable battery the active material is represented by the formula A a M b (XY 4 ) c Z d wherein a is from 0.1 to 6, b is from about 0.8 to about 3, c is from 1 to 3, and d is from 0 to 6; A is an alkali metal or mixture of alkali metals; M comprises at least one transition metal capable of being oxidized to a higher oxidation state than in the active material; Z represents a halogen, hydroxide, or combination thereof; and XY 4 is selected from the group consisting of X′O 4−x Y′ x , X′O 4−y Y′ 2y , X″S 4 , and mixtures thereof, where X′ is selected from the group consisting of P, As, Sb, Si, Ge, V, S, and mixtures thereof; X″ is selected from the group consisting of P, As, Sb, Si, V, Ge and mixtures thereof; Y′ is halogen, N, or S; 0≦x<3; and 0<y<4, wherein the composition of M, XY 4 , A, and Z, and the values a, b, c and dare selected so as to maintain electroneutrality of the active material comprising forming a slurry comprising a liquid phase and a solid phase, wherein the liquid phase comprises a solvent, alkali metal ions, and at least one anion selected from the group consisting of: a) phosphate, b) hydrogen phosphate; and c) dihydrogen phosphate and the solid phase comprises at least one transition metal and a carbonaceous reducing material present in an amount sufficient to reduce a metal ion of one or more metal compounds of the slurry in a subsequent heating step wherein at least one metal ion present in the slurry is reduced by the carbonaceous material during the subsequent heating step.