Synthesis of LiFe_0.5Mn_0.5PO₄/V/C Composites from Iron Phosphate Prepared Under Various Conditions and Its Performance for Lithium-Ion Battery Cathode

Synthesis of LiFe0.5Mn0.5PO4/V/C (LFMP/V/C) composites from various iron phosphate precursors and used it as lithium-ion battery cathode has been carried out. Iron phosphate was firstly prepared via wet chemical route by mixing C6H8O7 and FeSO4.7H2O in H3PO4 and NH4H2PO4 under different conditions. Characterization showed that the iron phosphate synthesized under different conditions resulted in different morphology and structure. Iron phosphate synthesized with no hydrothermal treatment resulted in aggregated particles, whereas the one subjected to ultrasonic treatment formed an octahedral-like morphology. Different pH conditions also affected the morphology and crystal structure of the iron phosphate. The morphology of the iron phosphate obtained in acidic condition was mixed between round and octahedral, in neutral condition was rectangular, and in basic condition was in flower-like shaped. The crystal in acidic condition favored lipscombite structure, while in the neutral and basic conditions favored phosphate iron salt structure. The LFMP/V/C composites were further obtained by mixing the prepared iron phosphate with LiOH, MnSO4.H2O, and NH4VO3, and conductive carbon through a solid-state reaction method. The best conductivity of 5.6870 x 10^-5 S.cm^-1 and working voltage of 4.7 V was obtained from LFMP/V/C fabricated from the precursor synthesized under basic atmosphere followed by hydrothermal and ultrasonic treatment.