Honeycomb-like biomass carbon with planted CoNi₃ alloys to form hierarchical composites for high-performance...

It is a significant challenge to combine a large pseudocapacitive material with conductive honeycomb-like carbon frameworks for long-term stable supercapacitors. Herein, hierarchical composite materials are manufactured by using biomass carbon, ZIF-67, and a mild pore former (Ni(CH₃COO)₂) to generate alloy-type CoNi₃ nanoparticles planted into conductive honeycomb-like carbon frameworks (C@ZIF-67-T). Meanwhile, the effect of carbonization temperature on the honeycomb-like pore size and the structure of composite materials is systematically investigated. As the honeycomb-like carbon skeleton structure guarantees good ionic and electronic conductivities and a large contact area, whereas the alloy nanoparticles provide a rich redox reaction for Faradaic capacitance. Therefore, the as-obtained C@ZIF-67-600 electrode presents a remarkable specific capacitance of 1044.8 F · g^-1 at 1.0 A · g^-1 and an ultra-long cycling stability with 30,000 cycles at 5.0 A · g^-1 in a three-electrode system. In addition, the assembled C@ZIF-67-600//activated carbon asymmetrical supercapacitor exhibit a high specific capacitance of 274.4F · g^-1 at 1.0 A · g^-1 and a long-term stable lifespan with a capacitance retention of 87% after 20,000 cycles at 5.0 A · g^-1. Besides, the asymmetrical supercapacitor also presents a maximum energy density of 85.13 Wh · kg^-1 at a power density of 750 W · kg^-1. Such superior electrochemical performance demonstrate that the designed electrode material provides a promising energy storage application.