Patent ID: 7285260

Claim:
A method for the synthesis of a compound of the formula Li x M 1−y M′ y (XO 4 ) n , wherein x, y and n are numbers such that 0≦x≦2, 0≦y≦0.6, and 1≦n≦1.5, M is a transition metal or a mixture of transition metals in the first line of the periodic table, M′ is an element with fixed valency selected from the group consisting of Mg 2+ , Ca 2+ , Al 3+ , Zn 2+ , and combinations thereof and X is S, P or Si, comprising: bringing into equilibrium in a reaction medium, in the required proportions, a mixture comprising the following precursors: a) a source of M, wherein at least one part of the transition metal or metals that constitute M are in an oxidation state greater than that of the transition metal or metals in the final compound Li x M 1−y M′ y (XO 4 ) n ; b) a source of an element M′; c) a compound that is a source of lithium; and optionally, d) a compound that is a source of X, wherein the sources of elements M, M′, Li and X are introduced, in whole or in part, in the form of compounds having more than one source element, and wherein the synthesis is carried out by reaction and bringing into equilibrium, in the absence of carbon or in the presence of an amount of carbon insufficient or too inert kinetically to realize the reduction of a metal salt that constitutes M, in the proportions required, the mixture of the precursors a) to d) and by reduction, with a reducing gaseous atmosphere, to bring the transition metal or metals to the desired degree of valency.