Mechanically exfoliated graphite paper with layered microstructures for enhancing flexible electrochemical energy storage

Abstract

Superior electrochemical properties and high flexibility are two crucial requirements and challenges for electrochemical capacitors (ECs) applied in flexible and wearable electronics. Here a low-cost and scalable method is proposed for the fabrication of mechanically exfoliated graphite paper (MEGP), which shows unique layered microstructures. The MEGP is subsequently used as a current collector to directly load multi-walled carbon nanotube@polypyrrole (MWCNT@PPy) core–shell hybrids as active materials, by electro-codeposition. The resultant MEGP/MWCNT@PPy electrodes demonstrate substantially enhanced electrochemical properties compared to GP/MWCNT@PPy, owing to the 3D interface constructed between layered MEGP and MWCNT@PPy. The symmetrical EC assembled using MEGP/MWCNT@PPy electrodes achieves an areal capacitance of 101.5 mF cm⁻² at a current density of 0.5 mA cm⁻², and an ideal rate capability. It also shows an electrochemical stability of 87.1% after 10 000 cycles, and retains 95.1% of the initial capacitance after enduring harsh mechanical deformation 400 times. These results indicate that the EC device has superior electrochemical properties and high flexibility with great potential for utilization in flexible and wearable electronic devices. The MEGP we have developed not only ensures the high flexibility of the device, but also boosts its electrochemical performance.