Prussian blue based vertical graphene 3D structures for high frequency electrochemical capacitors

Abstract Kilohertz high frequency electrochemical capacitors (HF-ECs), with a compact size, are being actively investigated with the aim for line-frequency ripple current filtering and other applications. However, the reported performance, particularly achievable capacitance density, the frequency response, and the phase angle that are directly determined by the electrode structure is still far from satisfactory that hinders its practical application prospect. In this work, metal organic framework (Prussian Blue, PB) is introduced as a structural mediator to develop three-dimensional vertical graphene architecture, or edge-oriented graphene (EOG) on a current collector via a 5-min rapid plasma carbonization and deposition process. With several prominent merits integrated together in the resulted EOG electrode structure, HF-ECs exhibit very low equivalent series resistance (ESR) of 40 mΩ cm−2 and attractive cell capacitance of 1.02 mF cm−2 and phase angle of −85.9° or 2.34 mF cm−2 and -80.6° at 120 Hz, which are the best reported overall performances thus far. Integrated cell is also assembled to work higher voltage for line-frequency ripple filtering, with demonstrated excellent performance. This study provides a new method and structure for developing high-performance HF-ECs.