Preparation of size-controlled all-lignin based carbon nanospheres and their electrochemical performance in supercapacitor

Lignin, as the second most abundant biomass material in nature, is regarded as an ideal carbon precursor due to the presence of a larger amount of aromatic ring structural unit. Carbon nanospheres, as one of the vital members of carbon materials, are promising advanced materials for various areas. However, lignin-based carbon spheres suffered a complex fabrication process, high crosslinking between spheres, and non-adjustable micron size. Here, all-lignin based carbon nanospheres (LCNS) with tunable size and microstructure were prepared via self-assembly, stabilization treatment, and carbonization. Subsequently, their applications in supercapacitor electrode material were investigated. The results showed that the monodispersed, ordered, and regular carbon nanospheres could be constructed. The size of LCNS could be tuned ranging from 256 to 416 nm via changing the initial concentration of lignin between 0.5 and 2 mg mL−1. The as-prepared LCNS provided a specific surface area between 652 and 736 m2 g−1 through adjusting the size and microstructure. When the LCNS was assembled into the electrochemical capacitor, the LCNS electrode materials exhibited a high specific capacitance of 147 F g−1. Additionally, the LCNS-based symmetrical capacitor showed an ultralow characteristic relaxation time (0.86 s) and long cycle stability for 10,000 cycles. The capacitance properties could be regulated via reconciling the size of nanospheres and microstructure induced by carbonization temperature. The governable capacitance performance indicates that the as-prepared LCNS should be a promising candidate material for energy storage.