Enhancing the capacitance/discharge times of flexible graphene supercapacitors with ionic liquid/Li electrolytes

摘要

This work reports a novel method for the fabrication of supercapacitors (SCs) which employs flexible graphene electrodes (FGEs), an aqueous Li electrolyte, and a separator (semipermeable membrane) between electrodes. In some devices, the Li electrolyte was improved with the addition of BMIMBF4-an Ionic liquid (IL), which enhanced the gravimetric capacitance of the devices, reaching a maximum value of 1558 F/g. Moreover, the presence of the IL enhanced from 272 to 800 min the discharge time, which suggests that the SCs release their energy as slow as batteries. In addition, the thickness of the separator was increased from 200 to 400 mu m, which allows stabilizing the discharge time for at least 120 min. Thus, the proposed combination of FGEs and electrolytes will open the opportunity to develop SCs with discharge cycles comparable to Li-based batteries. (C) 2019 Elsevier B.V. All rights reserved.