Honeysuckle flowers-derived hierarchical porous carbon matching with ionic liquid electrolyte for high-energy supercapacitors

Abstract As an electrode material, biomass-derived porous carbon has been extensively investigated for supercapacitors (SCs) due to its abundant resources, low cost, and sustainability. It is an important strategy to boost the energy capacity of SCs by using high-capacitance electrodes and widening electrochemical stability potential window (ESPW). In this work, a carbon material with hierarchical porous structure has been prepared by using honeysuckle flowers as the raw material and KOH as the chemical activator. The porous size distribution can be easily controlled by regulating the dosage of KOH to match the size of ionic liquid (IL) electrolyte. The honeysuckle-derived carbon (HC) electrode material exhibits a high specific capacitance of 186 F g−1 at 1 A g−1 in 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4) IL electrolyte. Moreover, the assembled symmetric SCs can provide a high specific energy of 93 Wh kg−1 at a specific power of 954 W kg−1, and its specific energy still remains 64 Wh kg−1 at 23 kW kg−1. Benefiting from the persevering architecture, the fabricated SCs also show a superior cyclability (83% of its initial value after 7500 cycles). Consequently, the investigation proves honeysuckle flowers are a promising sustainable carbon source for producing efficient electrode materials of high-performance supercapacitors.