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 m 2 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 Li 2 SO 4 . 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.