Carbon electrodes with ionophobic characteristics in organic electrolyte for high-performance electric double-layer capacitors

Abstract

Activated carbon (AC) in organic electrolyte-based electric double-layer capacitors (EDLCs) usually suffers from low specific capacitance. Most studies on AC focus on improving its surface area and optimizing pore structures to enhance its electrochemical performance in EDLCs. Unfortunately, the interfacial microenvironment, which is composed of nanoporous carbon and the organic electrolyte confined in it, is always ignored. Herein, a simple and powerful strategy to create AC with an ionophobic surface is proposed to address the poor efficiency of the electric double-layer process. The polar C-F bonds formed in the AC material are characterized through near-edge X-ray absorption fine structure and X-ray photoelectron spectroscopy. The ionophobic characteristic of YP-F60s in an organic electrolyte is extensively studied via contact angle measurements and small-angle X-ray scattering spectroscopy. An EDLC constructed with YP-F60s as the electrode and 1 mol L−1 tetraethylammonium tetrafluoroborate/propylene carbonate as the electrolyte demonstrates high specific capacitance, low internal resistance, and excellent cycling stability. Our results successfully demonstrate the importance of the interfacial microenvironment of AC and its confined electrolyte to the electrochemical performance of EDLCs. Our work also offers new perspectives on the use of the CF4 plasma technique to fabricate low-cost superior carbon for EDLCs.