Framework structured Na4Mn4Ti5O18 as an electrode for Na-ion storage hybrid devices

Abstract

In this study, framework structured Na₄Mn₄Ti₅O₁₈ possessing S-shaped tunnels for sodium intercalation is reported as an electrode for hybrid sodium ion batteries. Galvanostatic cycling of Na₄Mn₄Ti₅O₁₈vs. Na in the voltage region from 1.5 V to 3.95 V exhibits a capacity of 102 mA h g⁻¹ at 0.1C rate corresponding to a specific capacitance of 149 F g⁻¹ with a capacity retention of 90% over 50 cycles. The electrochemical analysis using CV measurements revealed the charge storage involving intercalation and pseudocapacitance. For instance, total charge storage of 345 C g⁻¹ is observed at 0.01 mV s⁻¹, which is attributed to 63% intercalation and 37% capacitance. Na₄Mn₄Ti₅O₁₈ was also studied for sodium ion storage in an aqueous medium. It delivered a capacity of 36 mA h g⁻¹ (144 F g⁻¹) in the voltage window of 0–0.8 V.