Morphology controllable fabrication of lotus-like 3D porous carbon with oxygen doping for aqueous Zn-ion storage

Designed porous structure coupling with proper functional groups are of great importance in enhacing Zn-ion hybrid supercapacitors (ZIHSs) and the long-term cycling life. Herein, a biomass-derived three-dimensional (3D) porous carbon (LSPC-2) with lotus like network structure and oxygen containing groups was prepared by using lotus husk as precursor via a combination utilization of hydrothermal and KOH activation. The as assembled Zn//LSPC-2 ZIHSs exhibit remarkable overall performance, including a high specific capacity of 212 mA h g-1 at 0.1 A g-1, an impressive energy density of 124 Wh kg-1 at 34 W kg-1, and an exceptionally long cycle life (with 97% capacitance retention after 10,000 cycles at 10 A g-1). These outstanding characteristics primarily result from the unique 3D carbon frame structure, rich in C=O functional groups and large specific surface area, providing a concise mass transfer pathway, rapid kinetics, enhanced conductivity, and enlarged Zn2+ adsorption sites. Charge-discharge process mechanism studies show that the reversible chemical adsorption of Zn2+ occur on the C=O and COOH functional groups, thereby markedly augmenting the pseudocapacitance contribution.