Na3Zr2Si2PO12/cellulose acetate composite solid electrolyte unlocking high ionic conductivity and long cycle life in solid-state sodium batteries

Abstract

The development of high-performance composite solid electrolytes represents a critical pathway toward safe and durable solid-state sodium batteries, yet remains challenged by insufficient ionic conductivity and interfacial instability. We engineer a novel NASICON-based composite solid electrolyte through rational integration of Na₃Zr₂Si₂PO₁₂ ceramic particles with a cellulose acetate polymer matrix via a facile solution-casting approach. This Na₃Zr₂Si₂PO₁₂/cellulose acetate (NZSP/CA) composite electrolyte achieves a high room-temperature sodium-ion conductivity of 1.73 × 10⁻³ S cm⁻¹, among the most competitive values reported for sodium solid electrolytes, through synergistic effects between ceramic fast-ion conduction pathways and polymer-mediated interfacial enhancement. The composite architecture simultaneously enables great electrochemical stability (4.94 V vs. Na⁺/Na), an appealing cation transference number (t_Na⁺ = 0.706), and dendrite-suppressing mechanical robustness. When deployed in Na//Na₃V₂(PO₄)₃ full cells, the electrolyte demonstrates impressive cycling stability with 80% capacity retention after 800 cycles at 3C, while maintaining a high specific capacity of 110 mAh g⁻¹ at 0.3C. Crucially, the cellulose acetate matrix derived from renewable plants introduces scalable sustainability merits, including industrial compostability and cost-effectiveness, within a lab-validated framework, offering a viable pathway to replace conventional fluorinated polymers in eco-friendly solid-state battery designs. This work establishes a new paradigm for high-performance composite solid electrolytes through rational ceramic–polymer synergy, resolving critical interfacial engineering and cycling stability challenges for practical solid-state sodium battery systems.