Patent ID: 8586241

Claim:
A process for preparing at least one compound of formula (I) Li a-b M 1 b Fe 1-c M 2 c P d-e M 3 e O x (I), the process comprising (A) heating a mixture comprising: at least one lithium-comprising compound; at least one iron-comprising compound, in which iron has an oxidation state +3 and is selected from the group consisting of iron(II, III)oxide, iron(III)oxide, iron(III)-oxide hydroxide, and iron(III)hydroxide; optionally, at least one M 1 -comprising compound; optionally, at least one M 2 -comprising compound; optionally, at least one M 3 -comprising compound; and at least one reducing agent which is oxidized to at least one compound comprising at least one phosphorous atom in oxidation state +5, at a temperature of 100 to 500° C. and at an autogeneous pressure, to reduce Fe to an oxidation state +2, thereby obtaining a product mixture comprising the at least one compound of formula (I), Li a-b M 1 b Fe 1-c M 2 c P d-e M 3 e O x (I), wherein Fe has the oxidation state +2, M 1 is at least one selected from the group consisting of Na, K, Rb, and Cs, M 2 is Mn, Mg, Al, Ca, Ti, Co, Ni, Cr, or V, M 3 is Si, S, or a is 0.8-1.9, b is 0-0.3, c is 0-0.9, d is 0.8-1.9, e is 0-0.5, x is 1.0-8, depending on an amount and oxidation state of Li, M 1 , M 2 , P, M 3 , and the at least one compound of formula (I) is neutrally charged.