A new family of cathode materials for lithium cells with nominal stoichiometry Li3Fe2-xCrx(PO4)(3) (0 < x < 1), was successfully prepared by ion exchange reactions of Na3Fe2-xCrx(PO4)(3) . The chemical exchange process leads to the structural transition from the monoclinic to a rhombohedral phase with an open framework which facilitates lithium diffusion. Chromium substitution was evidenced by a decrease in cell parameters in both sodium and lithium phases. Fe-57 Mossbauer spectra revealed a decrease in the isomer shift on increasing Cr content. The partial substitution by low Cr contents improved the electrochemical performance of Li3Fe2-xCrx(PO4)(3) . Thus, Li3Fe2-xCrx(PO4)(3) reversibly inserted 1.7 Li ions per formula unit, delivering a specific capacity of 105 mAh/g after the first discharge. The low electrode impedance of Cr substituted compounds can be responsible for the improvement of the electrochemical behavior. (C) 2011 Elsevier Ltd. All rights reserved.