High-performance aqueous sodium-ion storage using bundled fiber-based electrodes

Abstract

Fiber-based small-scale energy storage devices, enabling high energy density and power densities are highly desirable for miniatured portable electronic devices. However, fiber-based supercapacitors have limitations in terms of energy density owing to their small and slender electrode architectures. In this work, we design high-performance bundled fiber-type supercapacitors using sodium-ion pre-intercalated manganese oxide on carbon fiber bundles (Na–MnO₂@CFBs) and palmyra fruit-derived porous carbon array electrodes. We used the electrodeposition method to pre-intercalate Na-ions in the void spaces of MnO₂ layers and form core–shell-type nanoarchitectures, which are favorable in elevating electrochemical active sites and pseudocapacitive charges. Specifically, core–shell Na–MnO₂@CFBs electrodes provide higher Na-ion energy storage with a maximum specific capacitance of 222.5 F g⁻¹ and a length capacitance of 13.3 mF cm⁻¹ in aqueous sodium sulfate electrolyte. The core–shell Na–MnO₂@CFBs electrode also exhibits excellent electrochemical stability (95.6%) because of their hierarchical nanoarchitectures and good structural durability. Furthermore, the fabricated bundled fiber-type asymmetric supercapacitor exhibited high energy (18.04 W h kg⁻¹) and power (5829.1 W kg⁻¹) densities with good cycling stability. These results showed that bundled fiber electrodes and pre-intercalated alkali cations in MnO₂ layered structures could be employed as promising potential electrodes for small-scale energy storage applications to achieve high energy and power densities.