Synthesis of ultrahigh-surface-area nitrogen-doped porous carbon materials from carboxymethyl cellulose based protic polyanion ionic liquids for high performance supercapacitors

Sustainable nitrogen-doped carbon materials with a high specific surface area and hierarchical pore structures have aroused extensive interest as promising electrode materials for supercapacitors. In this study, nitrogen and oxygen co-doped porous carbon materials with an ultrahigh surface area (up to 3657 m2 g−1), desirable pore size (up to 2.28 nm) and a high content of 5.88 at% oxygen and 1.11 at% nitrogen were prepared from carboxymethyl-based protic polyanion ionic liquids (CPPILs) via a carbonization and staged KOH activation method, taking the advantages of using both ionic liquids and biomass as precursors for the synthesis of carbon materials. The specific structural properties of the obtained carbon materials can be tuned via using different organic bases to prepare the CPPILs and different carbonization conditions. The as-prepared carbon materials have good electrochemical performance such as a relatively high gravimetric capacitance of up to 291 F g−1 (at 0.1 A g−1), a high energy density of 10.11 W h kg−1, a high power density of 26 W kg−1, and a super high cycling stability of ∼99.49% capacitance retention after 10 000 cycles, when used as electrode materials for symmetric supercapacitors in 6 M KOH electrolytes, indicating a bright application prospect in the field of energy storage.