High-performance Zn-ion hybrid supercapacitors based on biomass-derived hierarchical porous carbon through template-activated bifunctional induced and ice-crystal assisted strategy

As a highly desirable cathode material for Zn ion hybrid supercapacitors (ZHSCs), biomass-derived carbon precursor shrinks and collapses at elevated temperatures resulting in an impeded internal morphology, which severely hampers ion storage and transport. Herein, a unique porous carbon with multi-level pore structures is produced by a one-step carbonization-activation process. The Gelatin with rich functional groups is employed as the gel-state biomass precursor and the ZnCl2 acted as both a template and an activator. Furthermore, the growth of ice crystals during freeze-drying prevents the carbon framework from collapsing and self-polymerizing of ZnCl2, endowing the prepared porous carbon with a high specific surface area (1336 m2/g) and inheritance of biomass precursor heteroatoms (including N and O). Therefore, at 0.5 A/g, the prepared material displays a desirable specific capacitance of 337.6 F/g in 6 M KOH. In particular, the assembled ZHSC simultaneously shows excellent cycling performance (after 10000 cycles, the specific capacitance increases to 95.6% at 10 A/g) and high energy and power density (120.1 Wh/kg at 450 W/kg). This work provides important insights for the facile preparation of electrode materials for high-performance ZHSCs.