Efficient Recycling of Sodium Superionic Conductor Electrolyte Enabled by NaF-Assisted Resintering for Solid-State Sodium Batteries

Solid-state sodium metal batteries, leveraging high energy density, superior safety, and the abundance of Na, exhibit broad application prospects. However, the lag in recycling technologies for solid electrolytes severely constrains the resource circularity efficiency. This work proposes a green and efficient recycling strategy targeting a spent sodium superionic conductor (NASICON) electrolyte. By incorporation of NaF as a sintering aid, followed by high-temperature resintering, the successful regeneration of the crystal structure and electrochemical performance was achieved. The recycled NASICON retained a rhombohedral crystal structure. The addition of NaF effectively compensated for Na loss and simultaneously enhanced the relative density, reaching 94.7%. The recycled electrolyte exhibited an ionic conductivity of 1.62 × 10–3 S cm–1 at room temperature. Symmetric Na cells assembled with it achieved a critical current density of 1.05 mA cm–2 and demonstrated stable cycling for over 1000 h at 0.4 mA cm–2. Full cells assembled with Na3V2(PO4)3 cathode delivered a discharge specific capacity of 93.8 mAh g–1 at a high rate of 20C, with performance comparable to that of fresh electrolyte. This strategy not only provides an effective solution for recycling sodium-based solid electrolytes but also promotes the green and sustainable development of the solid-state battery.