Synthesis of Hierarchically Porous Nitrogen-Doped Carbon Nanosheets from Agaric for High-Performance Symmetric Supercapacitors

Hierarchically porous, nitrogen-doped, and interconnected carbon nanosheets (HPN-CS) have been prepared from agaric through a one-step method, that is, simultaneous carbonization, activation, and nitrogen-doping. Potassium hydroxide infiltrated into the cell walls of agaric acts as an in-built activating agent to induce a unique architecture of the resultant material. HPN-CS have average pore diameter of 2.6 nm, specific surface area of 1565.6 m2 g−1, and high volume fraction of macro/mesopores (71.7%). It is noted that a lot of micropores with the simple pore structure are homogeneously distributed on the interconnected carbon nanosheets. The symmetric supercapacitor based HPN-CS achieve a high operation voltage of 2.0 V and energy density of 27.2 Wh kg−1 (at a power density of 1 kW kg−1) in aqueous electrolyte of 2 m Li2SO4. Even at the power density of 50 kW kg−1 (50 times increase, a full charge–discharge within 3.2 s), energy density still holds at 20.8 Wh kg−1, indicating an excellent energy storage/release performance. In addition, the single device is able to easily light 60 light-emitting diodes (working voltage 2.0–2.2 V) in parallel after charging for only 10 s, showing an outstanding potential in the practical applications.