Fluoride Ion Conductivity of Rb Doped KSbF4

All solid-state fluoride ion batteries are considered to be high energy density and safe energy storages. However, the F- ion conductivities of solid electrolytes at room temperature are significantly low (<10(-6 )S cm(-1)), which requires the higher operating temperature of fluoride ion battery such as 420 K or higher. Therefore, the faster F- ion conductors is strongly desired to operate fluoride ion battery at lower or even room temperature. KSbF4 is one of the promising candidates to have a faster F- ion conductivity. To expand F- ion conduction pathways, we doped Rb in KSbF4 and further investigated the compositional dependence of ionic conductivity in K1-x Rb x SbF4 system. We found that ionic conductivity strongly depends on the chemical composition and conductivity was maximized at x = 0.15. At room temperature, the F- ion conductivity in the bulk and at the grain boundary of K0.85Rb0.15SbF4 were sigma (bulk) = 1.01 x 10(-4 )S cm(-1) and sigma (GB) = 4.80 x 10(-5 )S cm(-1), respectively.

Automated summary

All-solid-state fluoride ion batteries are highly regarded for their high energy density and safety. However, the low F- ion conductivities of solid electrolytes at room temperature necessitate higher operating temperatures. KSbF4 doped with Rb has shown promise as a faster F- ion conductor. The ionic conductivity of K1-x Rb x SbF4 system strongly depends on the chemical composition, with maximum conductivity observed at x = 0.15. The F- ion conductivity in K0.85Rb0.15SbF4 was measured to be sigma (bulk) = 1.01 x 10(-4 )S cm(-1) and sigma (GB) = 4.80 x 10(-5 )S cm(-1) at room temperature.