A facile route to synthesize sheet-like Na₂Ti₃O₇ with improved sodium storage properties

A high purity sheet-like Na₂Ti₃O₇ material was synthesized by a new facile solid-state method with hollow sphere TiO₂ as titanium source. X-Ray diffraction(XRD) measurement proves that no impurity phase existed when the sample was heated at 900 °C. Charge/discharge measurement was performed in a potential range of 0.01–2.5 V at different current-rates(C-rates). The initial charge/discharge capacities are 191/424 mA·h/g at 0.1 C and still remain as high as 101 mA·h/g after 50 cycles. CV test proves that the large irreversible capacity in the initial cycle results from the formation of the solid electrolyte interface(SEI). However, the electrode presents an increased initial coulombic efficiency in a 1 mol/L NaPF₆ electrolyte compared to that in a 1 mol/L NaClO4 electrolyte.