PEO-NaPF₆ Blended Polymer Electrolyte for Solid State Sodium Battery

Solid-state polymer electrolytes (SPEs) are proposed as promising candidates for application in sodium batteries to replace the organic liquid electrolytes for enhanced safety. In this study, we first verified the feasibility of PEO-NaPF₆ SPE in solid-state sodium batteries (SSBs). The explored PEO-NaPF₆ SPEs exhibit a relatively high ionic conductivity of ∼6.3 × 10⁻⁴ S cm⁻¹ at 80 °C, a large Na⁺ transference number (t _Na+ ) of 0.58, and sufficient thermal stability at around 200 °C for SSBs. More importantly, the PEO-NaPF₆ SPEs afford excellent long-term cycling performances for the Na∣∣Na₃V₂(PO₄)₃@C cell at 80 °C (85.8% capacity retention at 2 C after 200 cycles) and the Na∣∣NaNi_2/9Cu_1/9Fe_1/3Mn_1/3O₂ cell at 80 °C (77% capacity retention at 0.5 C after 100 cycles). All of the properties make the PEO-NaPF₆ SPE a potential alternative for application in SSBs.