ZIF-Derived Carbon Microspheres for High-Performance Zinc-Ion Capacitors

In this work, we demonstrate the preparation of hierarchically porous carbon microspheres as cathodes for high-performance zinc-ion capacitors (ZICs) using ZIF-8-derived polymer composites as the template. Hydro/solvothermal treatment of ZIF-8 with tetrafluoroterephthalonitrile followed by carbonization yields carbon materials with a high specific surface area (up to ∼2000 m 2 g –1 ), hierarchical pore distribution, and large amount of heteroatom dopants. The heterogeneous phases in polymer composites produced from the hydro/solvothermal process were found to be crucial for the hierarchical pore structure in carbon, allowing fast electrolyte ion diffusion. In addition, the trace amounts of zinc compounds trapped in carbon could induce pseudocapacitance, thus promoting the electrochemical performance. As a result, the as-prepared ZICs displayed a maximum specific capacitance of 171.9 mAh g –1, a high energy density of 141.3 Wh kg –1, and a discharge capacitance retention of >95% (at 5000 cycles at 6 A g –1 ). This polymer composite-templated protocol provides a platform for the preparation of carbon materials for electrochemical energy storage and conversion applications.