Lithium ion battery applications such as transportation or renewable energies require cost effective, environmentally friendly and high capacity materials. Conversion reaction with iron based materials at positive electrode is a promising route to reach this target. In this work, iron hydroxyl-fluoride conversion coatings are prepared by an electrochemical way. The structure of the produced coatings is nano-porous with a pore diameter of about 75 nm. An impedance-based methodology is proposed for in-situ characterisation of the conversion coatings during the preparation procedure and enables to optimize the process parameters to get a 3D nano-porous structure. The cycling tests performed in coin-cell versus lithium reference electrode show a promising cycling behaviour for the prepared nano-porous coatings.