Exploiting various nanocarbons for supercapacitors with excellent energy retention under ultrahigh power output in high-voltage ionic liquid electrolytes possesses enormous potential for next-generation supercapacitor applications. To address the poor rate capability of the carbon electrodes in ionic liquid electrolytes, we develop an efficient strategy toward porous nanocarbons with controllable microstructure that fully solves this bottleneck to gain an outstanding capacitive performance. We found the introduction of laser-induced graphene and Mg as the additives can serve multiple roles not only as the morphology modifier agents but also as the template for the developing rich mesopores. In particular, a curved nanosheet network-like porous carbons constructed by nanocages with ultrahigh specific surface area and considerable amount of mesopores can be rationally obtained. When served as an electrode for ionic liquid-based supercapacitor, it can display an impressive specific capacitance of 201.1 F/g at 1 A/g, superb rate performance (71% capacitance retained at 100 A/g) and encouraging energy density up to 60.76 Wh/kg at a recording power density of 87.5 kW/kg, which is comparable with the best results reported for carbon-based supercapacitors in ionic liquid electrolyte reported so far.