Enhanced electrochemical performance of all-solid-state sodium-sulfur batteries by PEO-NaCF 3 SO 3 -MIL-53(Al) solid electrolyte

A flexible PEO-NaCF 3 SO 3 -MIL-53(Al) solid electrolyte is fabricated for all-solid-state sodium-sulfur batteries (ASSBs). When the mole ratio of EO (ethylene oxide of PEO):Na (sodium ion of NaCF 3 SO 3 ) is 20 and MIL-53(Al) is 3.24 wt%, high ionic conductivities of 6.87 × 10 −5 S cm −1 at 60 °C and 6.52 × 10 −4 S cm −1 at 100 °C are achieved. And the sodium ion transference number is significantly increased to 0.40 from 0.13 compared to the PEO-NaCF 3 SO 3 solid electrolyte without MIL-53(Al). When it is assembled to ASSBs, the batteries obtain high capacity retention and reversible current-rate capability. At 0.1 C and 60 °C, the solid-state battery delivers the first discharge capacity of 897.7 mAh g −1 and 674.9 mAh g −1 after 50 cycles with a coulombic efficiency near 100%. The enhanced electrochemical performances of the solid electrolyte, as well as ASSBs, are benefited from MIL-53(Al) filler.