Lignin, a type of abundant and low-cost biomass, is successfully utilized as a carbon precursor to prepare carbon nanosheets (CNSs) by freeze-casting of a lignin aqueous dispersion followed by direct carbonization without any activating treatment. The size and specific area of the obtained lignin-derived CNSs can be manipulated by controlling the concentrations of lignin aqueous dispersions, which in turn influences the graphitization degree of the CNSs as confirmed by wide angle X-ray scattering analysis and Raman spectroscopy. X-ray photoelectron spectroscopy study indicates that the CNSs contain ∼11–16 at% oxygen heteroatoms, which contribute to additional pseudocapacitance. The three-electrode supercapacitors based on optimized CNSs show a high capacitance of 281 F g⁻¹ at 0.5 A g⁻¹current density and good cycling stability in H₂SO₄ aqueous electrolyte. The study provides a simple, inexpensive, and environmentally friendly method for preparation of CNSs from various water-soluble biomass carbon precursors.

Using ionic liquid-loaded SiO₂-on-P(VDF–HFP) nanofibrous mats as electrolytes, both electrochromic devices and Li/LiCoO₂ batteries exhibit significantly improved performance.