Electrochemical performance of sol-gel-made Na 2 Ti 3 O 7 anode material for Na-ion batteries

Nanocrystalline Na 2 Ti 3 O 7 material is prepared by a newly developed sol-gel procedure. The sol-gel made Na 2 Ti 3 O 7 calcined at 500 °C possesses mesoporous structure and BET surface area of 89 m 2 g −1 . X-ray diffraction and scanning electron microscopy confirm the presence of sintered nanosheets or very small crystals of the size of 10–20 nm with short-range ordering. Electrochemical behavior of nanocrystalline Na 2 Ti 3 O 7 is evaluated by cyclic voltammetry of Na insertion and by galvanostatic chronopotentiometry at different charging rates. The sol-gel made Na 2 Ti 3 O 7 exhibits improved performance as compared to that of the microcrystalline Na 2 Ti 3 O 7 prepared by solid-state synthesis. Discharge capacities of optimized material at charging rates 1, 2, and 5C reach 109, 86, and 63 mAh g −1 , respectively, with 100% coulombic efficiency and zero capacity drop over 50 cycles after initial conditioning. Excellent performance of Na 2 Ti 3 O 7 _500 is obviously an effect of its large surface area giving rise to predominantly capacitive mechanism of charge storage. Hence, sol-gel made nanocrystalline Na 2 Ti 3 O 7 represents promising anode material for Na-ion batteries due to its charge capacity and outstanding cycling stability. Graphical abstract ᅟ