Ultrasound-assisted acid activation enables efficient plateau sodium storage in biomass-derived hard carbons

The prevailing strategy to enhance the sodium storage capabilities of biomass-derived hard carbon involves component modulation of lignocellulosic precursors through tailored pretreatment protocols. However, the existing methodologies suffer from operational complexity. This work presents a synergistic ultrasonication-HCl pretreatment strategy that promotes lignin depletion and cavitation-induced nanopore templating in ramie precursors. This dual-action approach promotes (i) turbostratic domain formation via lignin removal, (ii) cavitation-mediated matrix etching to produce disordered carbon frameworks, and (iii) thermal-driven pore closure during carbonization. The optimized anode delivers a remarkable reversible capacity of 331.8 mA h g −1 at 0.1C, with the plateau capacity reaching 62 % of the total capacity. When paired with a Na₃V₂(PO₄)₃ cathode, the full cell achieves an energy density of 227.9 Wh kg −1 (based on both cathode and anode mass).