Boosting aqueous Zn2+storage by engineering N, O co-doped 3D cheese-like hierarchical porous carbon

In light of large annual output and easy gathering, expired foods are regarded as a potential biomass to produce high value-added carbon cathodes in large scale for Zn-ion hybrid supercapacitors (ZIHSCs). Herein, inspired by the composition rich in protein and spongy scaffolding framework, the recycled carbon source of expired waffles is converted into 3D cheese-like hierarchical porous carbon doped by N, O dual-heteroatoms, together with high surface area and ample interconnected multiscale channels, plentiful nano-sized graphene layers plus preferable wettability towards aqueous electrolyte, therefrom making for numerous accessible active sites, fast kinetics and robust 3D network. As a result, the assembled aqueous coin-type ZIHSC device achieves a wondrous capacity of 214.4 mAh g- 1 at 0.1 A g- 1 with a marvelous conserved capacity of 94.7 mAh g- 1 by magnifying the current density to 50 A g- 1 and irresistible energy/power outputs of 171.2 Wh kg-1/42 kW kg- 1 plus an illustrious durability of 95.6 % capacity conservation over 20000 cycles at 20 A g-1. Significantly, the assembled quasi-solid ZIHSC device gives a surprising energy storage capability (a capacity of 154.9 mAh g-1, an energy output of 121.0 Wh kg-1, along with excellent flexibility and a low self-discharge rate of 2.75 mV h-1).