Surface‐Wrinkle‐Modified Graphite Felt with High Effectiveness for Vanadium Redox Flow Batteries

Abstract Surface‐wrinkle‐modified graphite felt (GF) with abundant N and O is prefabricated by a hydrothermal method followed by calcination, and its surface morphology, elemental composition, and electrochemical properties are characterized by scanning electron microscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge tests. The highly folded coating has excellent wettability, abundant catalytic sites, a fast ion‐diffusion rate, ultralow interface transfer resistance, and high catalytic activity for VO 2+ /VO 2 + and V 2+ /V 3+ reaction couples. Compared with the original GF, the modified GF greatly increases the redox reversibility of the VO 2+ /VO 2 + and V 2+ /V 3+ couples according to cyclic voltammetry profiles. The cathodic and anodic peak potential difference for VO 2+ /VO 2 + substantially decreases from 542 to 388 mV. A battery based on surface‐wrinkle‐modified GF exhibits overall improved efficiency, higher power density, and a high reversible efficiency with a stable average energy efficiency of 78% at a current density of 150 mA cm −2 for 200 charge/discharge cycles.