New comprehensions on structure superiority of asymmetric carbon membrane and controlled construction of advanced hierarchical inner-structure for high performance supercapacitors

Abstract

In this study, both asymmetric and symmetric carbon membranes are designed and fabricated through liquid-liquid phase separation and solvent evaporation, respectively. In contrast, asymmetric carbon membrane exhibits asymmetric porous structure with 3 D nanoscaled architecture, which facilitates ion transportation by shortening diffusion pathways for charging and discharging process. Meanwhile, PEG is introduced into the casting solution to mediate the pore size to a rational range and enhance the surface area. When the ratio of PEG is 10 wt%, the carbon membrane shows the highest specific surface area and hierarchical porous size. A maximum specific capacitance of 247 F g−1 is achieved at the current density of 0.5 A g−1 with good rate capability in an aqueous electrolyte of 6 mol L−1 KOH within the potential range of −1 to 0 V. Moreover, symmetric supercapacitors device assembled with the prepared carbon membrane achieved high energy density (9 W h kg−1) and power density (400 W kg−1) in 1 M Na2SO4 solution. The high electrochemical performance reveals the advantage of the rational micropore structure, and the asymmetric membrane architecture rose by fast solvents exchanging during phase-separation.