Facile fabrication of porous carbon film/Ni foil double-layer structure for high-rate and high-power flexible electrochemical capacitor

•Porous carbon film/Ni (PCF/Ni) is prepared by ambient pressure CVD followed by partial etching of Ni foil.•Thickness of PCF can be easily controlled by chemical etching time.•PCF/Ni exhibits high-quality interfacial contact and rich pore structure.•Ultrathin flexible electrochemical capacitors have good electrochemical performance and high power density.

A facile method has been developed to prepare flexible and uniform porous carbon film/Ni (PCF/Ni) double-layer structure for simply and rapidly assembling flexible electrochemical capacitor (EC). The PCF/Ni is obtained by ambient pressure chemical vapor deposition and subsequent partial etching of Ni foil. The thickness of PCF can be controlled by etching time. The PCF has a porous structure and tightly interface with Ni, resulting in a good conductivity and large surface area. The ECs based on PCF/Ni exhibits good electrical properties. Area (volumetric) capacitance of PCF/Ni electrode with PCF thickness of 0.52 μm reaches 0.31 mF/cm2 (5.96 F/cm3) at scan rate of 50 mV/s. Maximum volumetric (gravimetric) power density reaches 2.72 W/cm3 (9.05 kW/kg). The performance can be further improved by increasing the PCF thickness. Furthermore, the EC based on PCF/Ni has a very short time constant (~ 170 μs) and allows for operations at high rate up to 500 V/s.

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