title: Li(x)FeF6 (x = 2, 3, 4) battery materials: structural, electronic and lithium diffusion properties.
abstract: Lithium iron fluoride materials have attracted recent interest as cathode materials for lithium ion batteries. The electrochemical properties of the high energy density Li(x)FeF6 (x = 2, 3, 4) materials have been evaluated using a combination of potential-based and DFT computational methods. Voltages of 6.1 V and 3.0 V are found for lithium intercalation from Li2FeF6 to α-Li3FeF6 and α-Li3FeF6 to Li4FeF6 respectively. The calculated density of states indicate that Li2FeF6 possesses metallic states that become strongly insulating after lithium intercalation to form α-Li3FeF6. The large energy gain associated with this metal-insulator transition is likely to contribute to the associated large voltage of 6.1 V. Molecular dynamics simulations of lithium diffusion in α-Li3FeF6 at typical battery operating temperatures indicate high lithium-ion mobility with low activation barriers. These results suggest the potential for good rate performance of lithium iron fluoride cathode materials.
authors.affiliation: MEET Battery Research Center, Corrensstr. 46, 48149 Münster, Germany. melanie.schroeder@uni-muenster,de.
authors.forename: Melanie
authors.initials: M
authors.lastname: Schroeder
authors.forename: Christopher
authors.initials: C
authors.lastname: Eames
authors.forename: David A
authors.initials: DA
authors.lastname: Tompsett
authors.forename: Georg
authors.initials: G
authors.lastname: Lieser
authors.forename: M Saiful
authors.initials: MS
authors.lastname: Islam