3D connected porous structure hard carbon derived from paulownia xylem for high rate performance sodium ion battery anode

Biomass-derived hard carbon has garnered significant attention due to its high capacity, low cost and abundant resources. However, the application of biomass hard carbon is limited by the low initial coulombic efficiency and rate capability. Based on these issues, natural fortune paulownia wood with numerous pores has been used as the precursor to investigate the effects on initial coulombic efficiency and rate capability at different heating temperatures. As the heating temperature increased from 1000 °C to 1400 °C, the graphitization degree of the prepared hard carbon gradually increased, and the defect concentration gradually decreased, resulting in an increase in ICE from 76.8 % to 85.9 %, and a significant increase in the proportion of platform capacity from 49 % to 69 %. The prepared HC-1400 exhibits a reversible capacity of 313 mAh g−1 at 0.1 C, and can still achieve a capacity retention rate of 92 % after 500 cycles at 1 C (charge) and 5 C (discharge). Meanwhile, due to the excellent inheritance of the 3D connected porous structure of paulownia xylem, the prepared hard carbon even exhibits an excellent capacity of 209 mAh g−1 at 10 C. In addition, the assembled HC-1400||Na3V2(PO4)3 full battery also demonstrated a high energy density of 204.4 Wh kg−1 at 0.5 C, and still exhibited 116.6 Wh kg−1 even at a high rate of 10 C. This study will provide strong guidance for designing and preparing hard carbon with both high capacity and high rate performance for sodium-ion batteries anode.