Synthesis and electrode performance of carbon coated Na2FePO4F for rechargeable Na batteries

Abstract Carbon-coated Na 2 FePO 4 F is synthesized by a simple solid-state method with ascorbic acid as carbon source. Structural characterization of Na 2 FePO 4 F by synchrotron X-ray diffraction, scanning/transmission electron microscopy, and Raman spectroscopy reveals that ascorbic acid effectively suppresses the particle growth of Na 2 FePO 4 F, forming the nano-sized carbon coated materials. Electrode performance of Na 2 FePO 4 F for rechargeable sodium batteries is also examined. The carbon-coated Na 2 FePO 4 F sample (1.3 wt% carbon) delivers initial discharge capacity of 110 mAh g -1 at a rate of 1/20 C (6.2 mA g -1 ) with well-defined voltage plateaus at 3.06 and 2.91 V vs. Na metal. The sample also shows acceptable capacity retention and rate capability as the positive electrode materials for rechargeable Na batteries, which is operable at room temperature.