Bundled carbon nanofiber arrays grown on Cu-Ni tube textile boosting superior sodium-ion storage kinetics

Achieving high energy and power density in micro sodium-ion storage device is imperative and challenging due to the large radius of sodium ions and induced sluggish sodiation kinetics. Herein, we develop a vertically aligned carbon nanofiber arrays with a graphite dome (G-CNFAs/Textile) using the unique Cu-Ni solid solution textile as catalyst and thin substrate. As a flexible electrode with a maximum thickness of 4.0 µm, the G-CNFAs/Textile combines the merits of the thinner intertwined/ interconnected carbon nanofiber bundles, high porosity and abundant defects, thereby deriving enhanced sodium-ion storage kinetics. As a result, the flexible micrometer-scale G-CNFAs/Textile not only delivers an impressive gravimetric performance of 332.6 mA h g−1 at 1000 mA g−1 after 500 cycle numbers, but also exhibits outstanding volumetric capacity of ca. 1387.6 mA h cm−3 in half-type SIBs. Meanwhile, as the submicron-scale self-supporting symmetric electrode of SICs, the G-CNFAs//G-CNFAs capacitor also presents an impressive gravimetric capacitance of 66.5 F g−1 at 0.1 A g−1, superior energy-power density (80.9 W h kg−1 and 7771.8 W kg−1), as well as outstanding cyclic stability. Thus, we hope that this flexible micro-submicron-scale electrode structures could provide inspirations for thin, light-weight and miniaturized sodium-ion storage devices.