Upcycling water-soluble fraction from demolition wood fast pyrolysis bio-oil as a carbon coating precursor over graphite in lithium-ion batteries

The water-soluble fraction (W-SOL) of demolition wood fast pyrolysis bio-oil (FPBO) was evaluated as a bio-based carbon-coating precursor for graphite anodes in lithium-ion batteries. Graphite was coated by a simple aqueous mixing route using W-SOL solutions of varying concentration, enabling control of coating loading. The addition of a commercial surfactant had only a minor effect, indicating that W-SOL components can promote adsorption onto graphite without auxiliary additives.
Coating content was quantified by selective combustion thermogravimetry. After carbonization, Raman spectroscopy and N₂ physisorption showed formation of a disordered, porous carbon layer, with coating thickness, surface area, and porosity increasing with W-SOL concentration.
Electrochemical tests in lithium half-cells showed a strong dependence on coating loading. Low coating mass fractions gave the best performance, increasing delithiation capacity from ~322 to 335 mAh g⁻¹, lowering the average delithiation voltage from ~0.30 to 0.26 V, and extending cycle life at 20% capacity loss from ~50 to ~130 cycles. Initial coulombic efficiency decreased moderately with increasing coating content (84–87%), consistent with the higher surface area of thicker coatings. These results identify FPBO-derived W-SOL as a promising sustainable coating precursor for graphite and a valorization route for an underused bio-oil fraction.