In situ synthesis of a highly active Na2Ti3O7 nanosheet on an activated carbon fiber as an anode for high-energy density supercapacitors

This study proposes a unique hybrid structure with a one-dimensional activated carbon fiber (a uniform diameter of 300 nm) as a support for two-dimensional Na2Ti3O7 nanosheets (thickness of 20 nm) for a high-performance supercapacitor electrode (Na2Ti3O7/activated carbon fiber). With the important role of nanocomposites in improving electron and ion transportation, the Na2Ti3O7/activated carbon fiber displays a high specific capacity of 152 F g(-1) at 1 A g(-1), and a specific energy of 47.5 W h kg(-1) at a specific power of 900 W kg(-1) in the quasi-solid state supercapacitor with a voltage window of 0-1.6 V. Significantly, the sodium ion hybrid capacitor based on the Na2Ti3O7/activated carbon fiber nanocomposite as an anode and an active carbon fiber as a cathode exhibits a maximum specific capacitance of up to 76.8 F g(-1) at 1 A g(-1) and a high energy density of 127.73 W h kg(-1) at 95.79 W kg(-1) within a wide operating voltage of 3.0 V. The excellent electrochemical performance of the Na2Ti3O7/activated carbon fiber nanocomposite benefits from the facile diffusion of electrons and ions, and a high structural stability during the electrochemical process.