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

Abstract

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.