The present application relates to a process for the preparation of compounds of general formula (I) Lia-bM1bFe1-cM2cPd-eM3eOx  (I), wherein M1, M2, M3, a, b, c, d, e and x: M1: Na, K, Rb and/or Cs, M2: Mn, Mg, Ca, Ti, Co, Ni, Cr, V, M3: Si, S, a: 0.8-1.9, b: 0-0.3, c: 0-0.9, d: 0.8-1.9, e: 0-0.5, x: 1.0-8, depending on the amount and oxidation state of Li, M1, Fe, M2, P, M3, wherein compounds of general formula (I) are neutrally charged, comprising the following steps (A) providing an essentially aqueous mixture comprising at least one lithium-comprising compound, FeOOH as iron-comprising compound and at least one M1-comprising compound, if present, and/or at least one M2-comprising compound, if present, and/or least one M3-comprising compound, if present, at least one compound comprising at least one phosphorous atom and at least one reducing agent, (B) drying the mixture provided in step (A), in order to obtain a solid compound and (C) calcining the solid compound obtained from step (A) or (B) at a temperature of 300 to 950° C.