Flexible free-standing anodes of cobalt and carbon dot-coated porous carbon nanofibers for enhanced sodium-ion battery performance

Abstract

Flexible electrode materials have attracted attention due to their potential to expand the operational environments of sodium-ion batteries (SIBs). Herein, we successfully developed porous carbon nanofibers (CNF@CDs@CoOx) with favorable flexibility using an electrospinning method. This process utilized coal-based carbon dots as the precursor, polyacrylonitrile as spinning carrier and cobalt chloride as dopant. The resulting CNF@CDs@CoOx features a unique 3D cross-linked fiber network structure with rationally incorporated CoOx particles. This 3D architecture not only enhances the structural stability of the electrode materials but also allows the small and uniformly distributed CoOx particles to significantly improve the utilization of the active materials and endure the strain during Na⁺ insertion and extraction. The optimized CNF@CDs@CoOx-750 exhibits a suitable average diameter of 97 nm, a large specific surface area of 462.3 m² g⁻¹ and a rich nitrogen content of 9.67 wt%. Benefiting from these unique microstructural features, the CNF@CDs@CoOx-750 adopted as anode for SIBs displays prominent electrochemical features with high reversible capacity of 320 mAh·g⁻¹ at 20 mA·g⁻¹ and superior cycle stability, retaining 72 % of its capacitance after 400 cycles at 100 mA·g⁻¹. This study provides an effective strategy to prepare flexible electrode materials with high capacity and superior cycling performance, paving the way for advancements in anode materials for SIBs.