Facile Strategy to Low-Cost Synthesis of Hierarchically Porous, Active Carbon of High Graphitization for Energy Storage

To achieve high energy/power output, long serving life, and low cost of carbon-based electrodes for energy storage, we have developed a unique synthesis method for the fabrication of hierarchically porous carbon of high graphitization (HPCHG), derived from pyrolysis of an iron-containing organometallic precursor in a molten ZnCl₂ media at relatively low temperatures. The as-prepared HPCHG has a large specific surface area (>1200 m² g^-1), abundant micro/mesopores, and plenty of surface defects. When tested in a supercapacitor (SC), the HPCHG electrode delivers 248 F g^-1 at 0.5 A g^-1 and a high capacitance retention of 52.4% (130 F g^-1) at 50 A g^-1. When tested in a sodium-ion battery (SIB), the HPCHG electrode exhibits a reversible capacity of 322 mA h g^-1 at 100 mA g^-1 while maintaining ∼75% of the initial stable capacity after 2000 cycles with the applied current density as high as 5000 mA g^-1, implying that the HPCHG electrode is very promising for energy storage.