Hard Carbon Microtubes Made from Metaplexis japonica Seed Hair Fibers as High-Performance Anode Material for Sodium-Ion Batteries

Recycling and utilizing waste biomass for anode materials in sodium-ion batteries is significant for both environmental sustainability and economic efficiency. In this study, a biomass-derived hard carbon material (MJ-HCl-1400) with a three-dimensional hollow tubular structure was prepared from agricultural waste Metaplexis japonica seed hair fibers via a simple acid treatment. Benefiting from this unique hollow architecture and the structural optimization of the carbon layers through acid washing, MJ-HCl-1400 demonstrates improved electrolyte infiltration and accelerated ion diffusion. In addition, MJ-HCl-1400 developed a SEI abundant in inorganic constituents during cycling. As a result, MJ-HCl-1400 exhibits excellent rate performance and cycling stability, delivering a high capacity of 229 mAh g^–1 at 3 A g^–1 and retaining 84.1% of its capacity after 2000 cycles at 2 A g^–1. Additionally, the plateau capacity contributes over 65% of the total capacity across various current densities, indicating its stability even under high-rate conditions. This study proposes an efficient and affordable carbon-based option for energy storage applications.