UV-Cross-Linked Ionogels for All-Solid-State Rechargeable Sodium Batteries

A simple method to prepare a mechanically robust ionogel film by fast (<1 min) UV photopolymerization of poly­(ethylene glycol) diacrylate in the presence of an ionic liquid electrolyte based on N-propyl-N-methylpyrrolidinium bis­(fluorosulfonyl)­imide and sodium bis­(fluorosulfonyl)­imide is demonstrated. The ionogels showed very high ionic conductivity at 50 °C (6.5 × 10^–3 S·cm^–1) close to the liquid counterpart (7.8 × 10^–3 S·cm^–1). High salt concentration in the ionogels was beneficial for the sodium plating and stripping. Na/ionogel/NaFePO₄ full cells delivered a high specific capacity of 152 mAh g^–1 at 50 °C with good capacity retention.