Constructing monodisperse blueberry-like lignin-based porous carbon nanospheres for high-performance supercapacitors

Biomass-based porous carbon nanospheres are potential materials for energy storage because of their high specific surface area, environment-friendly, and abundant raw materials. Lignin is the most plentiful aromatic ring polymer in nature, which is the optimal candidate for developing porous carbon nanospheres. However, it is an enormous challenge to develop carbon nanospheres originated from lignin with uniform size, monodisperse and abundant pores. Herein, monodisperse blueberry-like lignin-based porous carbon nanospheres (ACS) are constructed through pre-carbonization and activation methods. The as-prepared ACS presents an adjustable specific surface area range of 557.9-2237.9 m2 g-1 and surface oxygen content of 5.5-8.48 at.%, which endows their excellent electrochemical performance with the capacitance of 254.2 F g-1 at 0.2 A g-1, energy density of 6.3 Wh kg- 1, as well as long cycle stability in 6 M KOH electrolyte. In comparison with all-lignin based carbon nanospheres without activation, the capacitance and energy density enhance around 1 time. When the ACS-based electrodes are assembled in 1 M Na2SO4 electrolyte, the voltage window enhances to 2 V, and the energy density is 22.4 Wh kg- 1, which elevates about 3.5 times compared with in KOH electrolyte. The relatively higher electrochemical behavior indicates that ACS derived from industrial waste can not only be a promising candidate for the application of energy storage, but also can solve the problem of waste of renewable resources.