Electrochemical studies on symmetric solid-state Na-ion full cell using Na₃V₂(PO₄)₃ electrodes and polymer composite electrolyte

Ubiquitous low-cost sodium ore is abundant and increasingly of interest for sodium-based battery research for grid-scale energy storage systems. The conventional organic liquid electrolytes in currently used sodium-based batteries endure inflammability, thermal instability, and risk of safety issues. The recent trend in developing solid-state-Li batteries also thrives on exploring the all-solid-state Na battery. Herein, we report a solid-state Na-ion full cell working at room temperature using a polyvinylidene fluoride (PVDF)-based composite polymer electrolyte and NaZr₂(PO₄)₃-structured Na₃V₂(PO₄)₃ (NVP) electrode. PVDF-based composite polymer electrolyte (CPE) with NaCF₃SO₃ salt and SiO₂ filler displays high conductivity with electrochemical stability. The symmetric solid-state full cell delivers a specific capacity of 76 mA h g⁻¹ at 0.5C rate, and a specific energy of 126 W h kg⁻¹ based on the total mass of the NVP cathode only. The solid-state Na-ion full cell can retain 70% of its initial specific capacity after 100 continuous charge-discharge cycles.