Abstract:
Sodium titanates (NTOs) are emerging as promising electrode materials for advanced energy storage devices, including sodium-ion batteries (SIBs), lithium- ion batteries (LIBs), and supercapacitors, owing to their favourable structural and electrochemical characteristics. Among various NTO phases, Sodium Hexa- Titanate (Na2Ti6O13) has gained particular interest due to its wide range of applications in energy storage devices. In this study, a novel, simplified, and cost- effective, greener solid-state synthesis method was developed to produce Na2Ti6O13 using naturally occurring rutile mineral sourced from Pulmoddai and Na2CO3 as precursors. The raw materials were mixed in a 1:6 molar ratio and subjected to mechanical activation through milling, followed by calcination at 800 °C. Phase identification via X-ray diffraction (XRD) confirmed the successful formation of single-phase Na2Ti6O13, indexed to JCPDS card No. 73– 1398. This indicates that the chosen stoichiometric conditions and processing parameters were effective in directing the complete transformation from the rutile precursor to the Na2Ti6O13 phase. Morphological analysis using scanning electron microscopy (SEM) revealed the formation of disorderly interconnected nanorods, with diameters ranging from 70 to 900 nm and lengths between 2 and 20 µm.
Electrochemical performance was evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV profile of the synthesised Na2Ti6O13 displayed broad redox peaks centred at ~0.4 V (cathodic) and ~0.7 V (anodic), corresponding to the reversible insertion/extraction of Na⁺ ions, while the rutile precursor showed no significant redox activity. EIS results of Na2Ti6O13 demonstrated enhanced ion diffusion characteristics and higher electrical conductivity. These findings demonstrate the viability of converting locally available rutile into a functional electrode material through an environmentally friendly and scalable process. The synthesised Na2Ti6O13 exhibited promising electrochemical behaviour, confirming its potential as an effective electrode material for SIBs, LIBs, and supercapacitor applications.
