title: Electrochemical studies of molybdate-doped LiFePO4 as a cathode material in Li-ion batteries.
abstract: The use of molybdate as a new anionic dopant that replaces phosphate in LiFePO4 was studied. When a small amount of molybdate (0.5 mol%) was used as a dopant, the olivine structure was maintained, while the lattice volume increased by 0.4%. The expanded volume facilitates ionic transfer, because of which the capacity of doped LiFePO4 at high current discharge rates is higher than that of pure LiFePO4. The discharge value increased by 25.2% at a charge rate of 5 C when the material was doped with 0.5 mol% molybdate ions. The slight expansion of the lattice volume in the olivine structure facilitates a fast redox reaction by lowering the charge transfer resistance. The current values from cyclic voltammetry indicate that the oxidation (charge) process of the cathode material is more improved than the corresponding reduction (discharge) process. Increasing the level of doping beyond 0.5 mol% had no effect on the results. At some discharge rates, the discharge capacity became worse. Because molybdate is divalent while phosphate is trivalent, a large number of molybdate ions in the lattice can exert considerable stress on the structure.
authors.affiliation: Department of Chemistry, Sangmyung University, Seoul 110-743, Republic of Korea.
authors.forename: Ketack
authors.initials: K
authors.lastname: Kim
authors.forename: Daewoong
authors.initials: D
authors.lastname: Kam
authors.forename: Yeonjoo
authors.initials: Y
authors.lastname: Kim
authors.forename: Sinwoong
authors.initials: S
authors.lastname: Kim
authors.forename: Minsoo
authors.initials: M
authors.lastname: Kim
authors.forename: Hyun-Soo
authors.initials: HS
authors.lastname: Kim
mesh_terms: D004553:Electric Conductivity; D011211:Electric Power Supplies; D004566:Electrodes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005290:Ferric Compounds / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D008422:Materials Testing; D008982:Molybdenum / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; C044659:molybdate; D008982:Molybdenum; D008094:Lithium; C035885:ferric phosphate