Ice template-assisting activation strategy to prepare biomass-derived porous carbon cages for high-performance Zn-ion hybrid supercapacitors

Biomass-derived porous carbons are desirable electrode material for supercapacitors, but the blocked carbon morphology leading to the poor accessibility and long diffusion distance hinders the practical application. Exposing the inner carbon space for smooth ion transport is crucial for the enhanced capacitive performance. Herein, porous carbon cages were prepared from heavy bio-oil using an ice template-assisting activation method. Ice crystals played crucial roles in the fabrication of cage-like morphology. By tuning the volume, ice crystals grew as templates to create cavities, prevent the shrinkage of carbon framework and transport activators into carbon bulks for high accessible surface area. The resultant porous carbons possess open structure with hollow cavities and layered shells, allowing the both excellent energy and power performance for symmetric super-capacitors and Zn-based hybrid supercapacitors. The assembled Zn-based hybrid supercapacitors achieve a favorable energy density of 119.02 Wh kg-1.