The present invention relates to a process for the preparation of compounds of general formula (I) Lia-bM1bV2-cM2c(PO4)x (I) with M1: Na, K, Rb and/or Cs, M2: Ti, Zr, Nb, Cr, Mn, Fe, Co, Ni, Al, Mg and/or Sc, a: 1.5-4.5, b: 0-0.6, c: 0-1.98 and x: number to equalize the charge of Li and V and M1 and/or M2, if present, wherein a−b is >0, by providing an essentially aqueous mixture comprising at least one lithium-comprising compound, at least one vanadium-comprising compound in which vanadium has the oxidation state +5 and/or +4, and at least one M1-comprising compound, if present, and/or at least one M2-comprising compound, if present, and at least one reducing agent which is oxidized to at least one compound comprising at least one phosphorous atom in oxidation state +5, drying and calcining.