Hierarchically Porous Carbon as a High-Rate and Long-Life Electrode Material for High-Performance Supercapacitors

In this study, cost-effective hierarchically porous carbon (HPC) derived from starch was successfully prepared through a simple mixing and subsequent one-step carbonization method. Based on the three-dimensional interconnected hierarchically porous structure, HPC exhibits a high specific surface area of 2259.54m(2)g(-1) and a specific capacitance of 385.7Fg(-1) at 1Ag(-1) in a three-electrode system. When the as-prepared carbon was employed to fabricate an aqueous symmetrical supercapacitor, the device displayed a high specific capacitance of 81.3Fg(-1) at 1Ag(-1), and even at 20Ag(-1) the specific capacitance remained 64Fg(-1) (capacity retention rate of 78.72% compares with that at 1Ag(-1)), demonstrating an outstanding rate performance. This supercapacitor maintained a capacity retention of 100% after 60000 cycles at a current density of 5Ag(-1), indicating superior long-term cycling stability. Furthermore, when the as-prepared carbon was employed to fabricate a symmetrical supercapacitor in ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIMBF4) electrolyte, it ultimately achieved an ultrahigh energy density of 133.94Whkg(-1) (power density of 1997.51Wkg(-1)) and a capacity retention rate of 83.3% was maintained after 5000 cycles throughout a wide operating potential window of 0-4V at 10Ag(-1).