An ionic liquid synthesis route for mixed-phase sodium titanate (Na2Ti3O7 and Na2Ti6O13) rods as an anode for sodium-ion batteries

Abstract

Sodium ion batteries represent a sustainable alternative to Li-ion technologies. Challenges with material properties remain, however, particularly with regards the performance of anodes. We report a rapid, energy-efficient ionic liquid synthesis method for mixed phase Na₂Ti₃O₇ and Na₂Ti₆O₁₃ rods. This method is based on a novel phase-transfer route which produces pure functional materials via a dehydrated IL. The structure of the synthesised materials was characterised using powder X-ray diffraction, which confirms the formation of a mixed Na₂Ti₃O₇ and Na₂Ti₆O₁₃ phase, with majority Na₂Ti₃O₇ phase, in contrast to previous synthesis methods. Scanning and transmission electron microscopy analysis reveals a rod morphology, with an average diameter and length of 87 nm ± 3 nm and 1.37 μm ± 0.07 μm, respectively. The initial discharge and charge capacity of Na₂Ti₃O₇ nanorods were measured as 325.20 mA h g⁻¹ and 149.07 mA h g⁻¹, respectively, at 10 mA g⁻¹ between 0.01–2.5 V. We attribute the enhanced performance to the higher weight fraction of Na₂Ti₃O₇ phase vs. previous reports, demonstrating the potential of the ionic liquid method when applied to sodium titanate materials.