The rising demand for large-scale, sustainable energy storage has accelerated research into
sodium-ion batteries (SIBs) as a cost-effective and safe alternative to lithium-ion systems.
Among various anode materials, Na2Ti3O7 stands out for its structural stability and favourable theoretical capacity. However, its practical application is hindered by poor electrical conductivity, sluggish sodium-ion diffusion, and structural changes during cycling.
Chapter 3 focused on the effects of thermal treatment on the structural evolution of Na2Ti3O7. By varying calcination temperatures, it was confirmed that structural changes previously attributed to symmetry transitions are predominantly caused by crystal growth. XRD and Raman analyses identified that 800 °C is the optimal temperature, achieving a balance between crystallinity, structural stability, and reasonable energy consumption.
Chapter 4 explored the effect of reduction treatments under H2/N2 atmospheres to produce reduced Na2Ti3O7 (RNTO). The presence of Ti3+ species introduced through controlled reduction substantially enhances conductivity and lowers activation energy, translating into superior electrochemical performance. After 100 cycles at 0.1 C, RNTO achieved a stable specific capacity of 94.27 mAh/g. Impedance spectroscopy confirmed improved conductivity, while maintaining structural integrity. At the same time, a rarely studied Na-Ti-O phase, Na0.8Ti4O8 was first time tested as anode material, and provided a stable cycle performance with less than 5 mAh/g specific capacity lost in 96 cycles.
Chapter 5 examined the effects of carbon coating on Na2Ti3O7 using polydopamine-derived carbon layers. TEM observations confirmed uniform and continuous coatings. Optimised carbon coating improved cycling performance and rate capability, with the best-performing samples retaining 82.23 mAh/g after 100 cycles compared to the pristine material’s 54.27 mAh/g. However, excessive carbon content induced phase transitions, highlighting the need for strict process control.
Overall, this work provides new insights into the structure–performance relationship of
Na2Ti3O7 and delivers practical synthesis guidance for scalable, cost-effective sodium-ion
battery anode development.
