Construction of three-dimensional nitrogen doped porous carbon flake electrodes for advanced potassium-ion hybrid...

It is of great significance to develop a new kind of green and environmentally friendly potassium ion energy storage device, with stable structures and large specific capacity. In this manuscript, a facile and robust way is reported to construct nitrogen doped porous carbon flake (NPCF) through NaCl template and pyrolysis method. 3D porous structures can be formed and interconnected NPCF are used as potassium ion batteries (PIBs) anode. High content of pyridinic N/pyrrolic N and enlarged interlayer distance of NPCF are obtained. Specifically, the anode delivers a high reversible capacity of 326.3 mAh g^-1 at the current density of 50 mA g^-1, and shows up outstanding cycle stability and represents long cycle life of 10,000 cycles at a current density of 5000 mA g^-1. Moreover, the cyclic voltammetry kinetic analysis shows that the main capacitive process plays a leading role in the potassium storage mechanism. Consequently, equipped with activate carbon (AC) as cathode and NPCF as anode, the assembled potassium ion hybrid capacitors (PIHCs) achieve an energy density of 65.8 Wh kg^-1 at 100 mA g^-1, and maintains 30 Wh kg^-1 even at a high current density of 5000 mA g^-1.