Synthesis and characterization of lithium transition orthosilicates Li2FexMn1-xSiO4 as cathode material

Recently, lithium metal orthosilicates Li₂FeSiO₄ and Li₂MnSiO₄ are attracted attention as a cathode material for Li-ion batteries. Here, Li₂Fe_xMn_1-xSiO₄ (x = 0.3, 0.5, 0.7) cathode materials are synthesized by using sol-gel method, and physically characterized via X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and Energy dispersive X-ray (EDX). The FESEM images confirm the cubical shape particles in nanometers scale. The EDX mapping indicates the presence of iron, manganese, and silicates in different samples. The Li-ion batteries are assembled with gel polymer electrolyte PVdF-HFP/LiClO₄/EC-PC, and Li₂Fe_xMn_1-xSiO₄ (x=0.3, 0.5, 0.7) cathode and graphite anode. The assembled cells are electrochemically characterized by cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD) techniques. It is observed that the oxidation and reduction peaks of the cells shifted as scan rate increases which indicate the charge transfers are diffusion controlled at the interface. The cell Li₂Fe_0.5Mn_0.5SiO₄//graphite offers highest discharge capacity∼220 mAh g⁻¹ at 1 mA cm⁻².