Toward High Performance All Solid-State Na Batteries: Investigation of Electrolytes Comprising NaPF6, Poly(ethylene oxide) and TiO2

Abstract

Solid electrolytes based on polyethylene oxide (PEO) have been studied for decades, owing to their facile and low-cost processing, good electrochemical stability, and excellent complexation with alkali metal salts. Complexes of PEO with appropriate sodium salts are well known for ionic conduction. Here, pristine NaPF6:P(EO)16 and a composite solid electrolyte containing TiO2 nanowires were investigated as candidates for rechargeable solid-state sodium batteries. Comprehensive electrochemical characterizations were carried out, including ionic conductivity, transference number, and structural stability. At elevated temperatures, the specific capacity of an all-solid-state Na3Ti2(PO4)3 (Na/NTP) sodium battery was 110 mAh g−1, higher than room-temperature cells with liquid electrolyte solutions. We attribute this behavior to increased conductivity of the polymer electrolyte, induced by the ceramic nanofiller, combined with enhanced electronic conductivity of the NTP cathode.