Boosting zinc-ion storage capability by engineering hierarchically porous nitrogen-doped carbon nanocage framework

In virtue of combining superb power of supercapacitors and high energy of batteries, zinc-ion hybrid supercapacitors become a competitive candidate in current energy storage systems. However, the cell chemistry related to carbon cathode still suffers from the obstacles of reaction kinetics and charge storage efficiency. Herein, a three-dimensional framework of N-doped carbon nanocages is constructed through pyrolyzing and activating polypyrrole on the platform of ZIF-8, synchronously achieving hierarchical porosity and high N-doping content. Thanks to the comprehensive modulation of the morphology, pore structure, and surface chemistry, the obtained carbon shows the significant enhancement in active site exposure and diffusion kinetics. Therefore, the zinc-ion hybrid supercapacitor using this carbon cathode achieves the remarkably improved Zn-ion storage capability (124 mAh g−1 at 0.25 A g−1 with a 65.9% capacity retention at 20 A g−1, and nearly no capacity decay after 10000 cycles at 10 A g−1). Moreover, this device exhibits superior energy/power densities of 107.3 Wh kg−1/16647.7 W kg−1, together with a low self-discharge rate of 3 mV h−1. Our work presents a good design strategy to develop advanced carbon-based cathodes to accelerate the development of Zn-based devices.