Tailored architecture of composite electrolyte for all-solid-state sodium batteries with superior rate performance and cycle life

Seeking for composite electrolytes reinforced all-solid-state sodium ion batteries with superior long lifespan and rate performance remains a great challenge. Here, a unique strategy to tailor the architecture of composite electrolyte via inserting polymer chains into a small quantity of sulfate sodium grafted C₄₈H₂₈O₃₂Zr₆ (UIOSNa) is proposed. The intimate contact between polymer segments and UIOSNa with limited pore size facilitates the anion immobilization of sodium salts and reduction of polymer crystallinity, thereby providing rapid ion conduction and reducing the adverse effect caused by the immigration of anions. The grafting of −SO₃Na groups on fillers allows the free movement of more sodium ions to further improve \({t_{{\rm{N}}{{\rm{a}}^ + }}}\) $$t_{{\text{Na}}^{+}}$$ and ionic conductivity. Consequently, even with the low content of UIOSNa fillers, a high ionic conductivity of 6.62 × 10⁻⁴ S·cm⁻¹ at 60 °C and a transference number of 0.67 for the special designed composite electrolyte are achieved. The assembled all-solid-state sodium cell exhibits a remarkable rate performance for 500 cycles with 95.96% capacity retention at a high current rate of 4 C. The corresponding pouch cell can stably work for 1000 cycles with 97.03% capacity retention at 1 C, which is superior to most of the reported composite electrolytes in the literature.