High-performance wearable asymmetric electrochemical capacitors based on composite aramid nonwovens with unique surface architecture

Abstract

High-performance flexible asymmetric electrochemical capacitors (ANW-AECs) for high energy-density wearable devices have been developed through assembling unique aramid nonwovens (ANWs) with different surface structures, that is, ANWs chemically coated with Ag particles and polypyrrole (ANW/Ag/PPy) act as a positive electrode, while ANWs chemically coated with Ag particles and multi-walled carbon nanotubes (ANW/Ag/CNT) play as a negative electrode. The influences of different compositions of surface modified ANWs on structure and integrated performances of ANW-AECs were intensively studied and compared with those of symmetric electrochemical capacitors (ANW-SECs). The prepared ANW-AECs not only have high energy density, but also process good wearability and cyclability. Their areal, volumetric or gravimetric energy density reaches 2.55 × 10−4 W h cm−2, 3.27 × 10−3 W h cm−3 or 8.61 × 10−3 W h g−1 at a high operating voltage of 1.6 V; their capacitance is still as high as 95.0% or 95.9% when the electrochemical or bending cycle reaches 1000 or 500. These outstanding performances originate from asymmetric design of devices as well as unique chemical and space structures of electrodes, including interactions between different components, high electrical conductivity and specific surface area.