Hydrothermal synthesis of K3FeF6 and its electrochemical characterization as cathode material for lithium-ion batteries

Abstract

K 3 FeF 6 was synthesized through a simple hydrothermal reaction for a novel cathode material of lithium-ion batteries. From the SEM and TEM images, the synthesized K 3 FeF 6 particle are about 30-50 nm after high energy ball milling. K 3 FeF 6 electrode delivers a high reversible capacity of 212.6 mAh g −1 and it maintained 131 mAh g −1 after 30 cycles. Additionally, in rate performance test, when the current density returns back to the 10 mA g −1 again, the full recovery of the capacity exhibits its superior rate performance. The electrochemical redox mechanism, herein studied through Ex-situ XRD of K 3 FeF 6 electrodes at different polarization voltages, shows the satisfactory reversibility of structure.

Fluorinated Materials as Positive Electrodes for Li- and Na-Ion Batteries

“…K 3 FeF 6 and Na 3 FeF 6 microcubes synthesized from a solvothermal synthesis were studied as cathodes for LIB and NIB and display good capacities and so-called reversibility, despite the lack of structure characterization. But voltage values obtained during the electrochemical processes could probably result from conversion reactions. , A recent combination of synchrotron X-ray diffraction and 23 Na/ 19 F solid-state nuclear magnetic resonance (NMR) confirms that Na 3 FeF 6 undergoes conversion into NaF and Fe(s) nanoparticles …”

“…But voltage values obtained during the electrochemical processes could probably result from conversion reactions. 73,74 A recent combination of synchrotron X-ray diffraction and 23 Na/ 19 F solid-state nuclear magnetic resonance (NMR) confirms that Na 3 FeF 6 undergoes conversion into NaF and Fe(s) nanoparticles. 75 Finally, it should be noted that a cryolite type Na 3 VOF 5 was recently synthesized by a solvothermal route at 200 °C.…”