Silicates LiMSiO4 are potential positive electrode materials for lithium ion batteries. In this work we analyse from first principles calculations the relative stability of possible LiFeSiO4-Polymorphs within four structural types. Olivine-LiFeSiO4 is predicted to be more stable than the LiFeSiO4 prepared by delithiation of Li2FeSiO4; the latter being the only LiFeSiO4 compound reported so far. Attempts to prepare olivine-LiFeSiO4 from a mixture of reactants at ambient pressure (600-1100 degrees C) resulted in a mixture of quartz-SiO2, Li2SiO3, LiFe5O8 and LiFeSi2O6 phases. Conducting the reaction under HP conditions (40 kbar) leads to the formation of LiFeSi2O6 as a majority phase, regardless the nature of the reactants/precursors. First principles calculations indicate that the preparation of the olivine-LiFeSiO4 is then-nodynamically hindered due to the competition with the more stable LiFeSi2O6 pyroxene, in the range of pressure/temperature investigated. (C) 2008 Elsevier B.V. All rights reserved.