Ionic liquid C16mimBF4 assisted synthesis of poly(benzoxazine-co-resol)-based hierarchically porous carbons with superior performance in supercapacitors

Hierarchically porous carbons with variable pore sizes at multi-length-scale, a nitrogen and boron co-doped and local graphitized framework, and high mechanical strength were synthesized through the self-assembly of poly(benzoxazine-co-resol) with ionic liquid C(16)mimBF(4) and a carbonization process. In this synthesis, the ionic liquid acts both as a structure directing agent and a heteroatom precursor. The obtained porous carbons have a specific surface area lower than 376 m(2) g(-1) and thus a high skeleton density. With such heteroatom doped skeleton structures and fully interconnected macropores, mesopores and micropores, the hierarchically porous carbon shows outstanding electrochemical performance, e.g. a superior high gravimetric capacitance (C-g) of 247 F g(-1), an interfacial capacitance (C-S) of 66 mu F cm(-2) (calculated based on the discharge curve with a constant current density of 0.5 A g(-1)), whilst a high volumetric capacitance (C-v) of 101 F cm(-3) compared to those reported in the literature. Cycling stability tests indicate that the carbon exhibits a capacitance retention of similar to 96.2% after 4000 charge-discharge cycles, strongly reflecting an excellent long-term cyclability of the electrode. Due to its unique skeleton structure and high conductivity, such hierarchically porous carbon shows promise as an electrode material for supercapacitors.