(134d) Metal Fluoride/Graphene Composites for High-Performance Li-Ion Cathodes

Rechargeable batteries with improved energy and power density have many potential, high impact applications including advanced portable electronics and electric vehicles.  However, most ‘next-generation’ materials capable of providing improved performance suffer from rapid capacity degradation or severe loss of capacity when rapidly discharged.  Graphene, a unique two-dimensional material composed of atomically thin carbon sheets, has shown potential to address unsatisfactory rate capability, limited cycling performance and abrupt failure of these high capacity material.  Therefore, we have been exploring graphene-based architectures, allowing us to exploit graphene’s unique combination of high surface area, high in-plane electrical conductivity, excellent tensile modulus and mechanical durability. 

Metal fluorides, including iron trifluoride (FeF₃), have the potential of both high energy delivery and high cyclability.  We have recently developed a stable nanostructured iron fluoride (FeF₃)/graphene composite cathode.  A facile route that combines co-assembly and photothermal reduction was developed to synthesize free-standing, flexible FeF₃/graphene papers. The papers contained a uniform dispersion of FeF₃ nanoparticles (< 40 nm) and open ion diffusion channels in the porous, conducting network of graphene sheets that resulted in a flexible paper cathode with high charge storage capacity, rate, and cycling performance, without the need for other carbon additives or binder.  The composites demonstrate promising applications as cathodes in high-energy density Li-ion batteries.  In a free-standing form, they showed a high storage capacity of >400 mAh/g and improved cycling performance compared to bare FeF₃ particles.  In addition, we have investigated a novel mixed metal fluoride cathode system, containing tunable manganese and iron fluoride, for which characterization and electrochemical performance will be presented.