Converting biomass tar into N-doped biochar: A promising anode material for enhanced sodium-ion batteries

Intensifying fossil fuel crisis has raised significant attention to the utilization of biomass energy, particularly biomass gasification technology, which is pivotal for its large-scale application. However, the generation of biomass tar during gasification remains a major obstacle. Due to the high carbon content of biomass tar and its compositional and property similarities to coal tar and pitch, this study explores the synthesis of nitrogen-doped biochar by combining urea with biomass tar, and evaluates its potential use as an anode material in sodium-ion batteries. The synthesized material, denoted as NT2–1000 (with a urea-to-biomass tar mass ratio of 2:1 and a carbonization temperature of 1000 °C), exhibited a reversible capacity of 257.49 mAh g⁻¹ at a current density of 25 mA g⁻¹, achieving an initial coulombic efficiency of 59.34 %. After 50 cycles at 50 mA g⁻¹, the capacity almost unchanged. At a higher current density of 1000 mA g⁻¹, the material retained 70.33 % of its initial capacity of over 200 cycles (122.6 mAh g⁻¹), demonstrating excellent rate capability and cycling stability, which is desirable for sodium-ion battery anodes. This research presents a novel method for valorizing carbon from biomass tar, thus promoting the high-value use of waste products generated in energy production processes.