Synthesis and Characterization of a LiFe_0.6Mn_0.4PO₄ Olivine Cathode for Application in a New Lithium Polymer Battery

Abstract A LiFe_0.6Mn_0.4PO₄ (LFMP) cathode exploiting the olivine structure is herein synthesized and characterized in terms of structure, morphology, and electrochemical features in a lithium cell. The material shows reversibility of the electrochemical process which evolves at 3.5 and 4 V versus Li⁺/Li due to the Fe⁺²/Fe⁺³ and Mn⁺²/Mn⁺³ redox couples, respectively, as determined by cyclic voltammetry. The LFMP has a well‐defined olivine structure revealed by X‐ray diffraction, a morphology consisting of submicron particle aggregated into micrometric clusters as indicated by scanning and transmission electron microscopy, with a carbon weight ratio of about 4% as suggested by thermogravimetry. The electrode is used in lithium cells subjected to galvanostatic cycling with a conventional liquid electrolyte, and demonstrates a maximum capacity of 130 mAh g⁻¹, satisfactory rate capability, excellent efficiency, and a stable trend. Therefore, the material is studied in a lithium metal polymer cell exploiting an electrolyte based on polyethylene glycol dimethyl ether with a solid configuration. The cell reveals very promising features in terms of capacity, efficiency, and retention, and suggests the LFMP material as a suitable electrode for polymer batteries characterized by increased energy density and remarkable safety.