Highly Ordered Micropores Activated Carbon from Long Fiber Biomass for High Energy Density Supercapacitors

The electrochemical performance of carbon based supercapacitors not only depends on the specific surface area and conductivity, but also the structure of materials. In order to construct the carbon materials with effective structure, the long fibrous plant-saussurea involucrata stalk was chosen as the new style carbon source. Highly ordered micropores activated carbon (HOMAC) materials have been successfully obtained via KOH chemical activation method. The synthesized HOMAC exhibits high specific surface area of 2692 m2 g−1 and pore volume of 1.14 cm3 g−1. The assembled HOMAC-based electrode can deliver a high specific capacitance of 379 F g−1 at 2 mV s−1 in 1 M H2SO4 aqueous electrolyte, and show excellent cyclic stability (the capacitance retention ∼95 %) over 10000 cycles at a current density of 1 A g−1, which authenticates excellent charge storage capacity of electrode material. Moreover, the operation voltage window can be expanded to 0–1.8 V in 1 M Na2SO4 electrolyte for the 2-electrode system. The symmetric supercapacitor can deliver a high energy density of 33.91 Wh kg−1 at power density of 180.03 W kg−1. These high performances can be ascribed to the high surface area and ordered microporous structures obtained using KOH as activator. We further discussed the relationship between fibrous plants and electrochemical performances of the final activated carbon materials. This present work can provide beneficial guidance for the preparation of high performance activated carbon electrodes from a biomass-based carbon source. Comparing with two different biomass materials, it can be found that the ionic diffusion coefficient of saussurea involucrata is 5.074×10−13 m2 s−1, which is 2.5 times of cotton stalk (1.547×10−13 m2 s−1). This phenomenon indicates the different ion transmission rate in different pore structures.