Facile sol-gel synthesis of LiMn0.5Fe0.5PO4 cathode materials fostered by bio-derived natural agar

Olivine-structured LiMn0.5Fe0.5PO4 cathode materials were successfully synthesized via the bio-derived agar-assisted sol-gel method. Rietveld analysis revealed that the structure of the synthesized materials was orthorhombic with the Pbnm space group. The addition of agar in the precursors significantly reduced the calcination temperature and impurity phases. When increasing the temperature from 400 to 700 degrees C, the particle size of LiMn0.5Fe0.5PO4 was increased from 1 to 3 mu m. Among all the samples, LiMn0.5Fe0.5PO4 synthesized with agar at 700 degrees C delivered better electrochemical performances due to its lower charge transfer resistance. The same sample exhibited specific discharge capacities of 143, 123, 110, 96, and 88 mAh/g at C/10, C/5, C/3, C/2, and 1C rates, respectively. The retention in capacity was observed to be 95% for 40 cycles at C/3 rate. The obtained results indicated the feasibility to synthesize phase pure LiMn0.5Fe0.5PO4 powders by the addition of agar.