Highly efficient utilization of polypyrrole enabled by dispersed buckypaper tape for high-performance flexible energy storage

Abstract

To construct flexible supercapacitors with highly efficient utilization of active materials for charge storage, as well as high structural stability against mechanical deformation, an anodic treatment process is proposed and demonstrated to disperse densely stacked carbon nanotubes (CNTs) in buckypaper tape (BPT). The as-prepared dispersed BPT (DBPT) features large interior space and hydrophilicity, which are thoroughly favorable for the efficient loading of polypyrrole (PPy) via the formation of core–shell CNT@PPy composite structures. This strategy eliminates the apparent interface existing between the active materials and the substrate of the BP/PPy electrode. The loading thickness of PPy is shown to decrease dramatically from 12 μm for BPT/PPy down to 320 nm for DBPT/PPy electrodes. Additionally, PPy shows both greater roughness and higher doping level when loaded onto DBPT. These characteristics result in significantly enhanced supercapacitive properties and high structural stability for DBPT/PPy. The areal capacitance of the DBPT/PPy electrode with high loading mass of PPy (3.26 mg cm⁻²) reaches 1112.6 mF cm⁻² at 1.0 mA cm⁻², more than twice that of BPT/PPy, which also has substantially boosted rate capability and cycling stability. The assembled flexible supercapacitor with DBPT/PPy electrodes retains 88.3% of its initial capacitance after 1000 cycles of bending to 180°, whereas that assembled with BPT/PPy electrodes maintains only 34.2%.