Flexible, all-solid-state supercapacitors derived from waste polyurethane foams

Recently, flexible energy storage devices have attracted increasing interests for their promise in wearable electronic devices. In this study, the waste polyurethane foam (WPUF), a common polymeric waste having caused considerable environmental pollutions, is employed for the first time in the fabrication of flexible electrodes through wrapping carbon nanotubes (CNTs) and cellulose nanofibers (CNFs), pressing into thin foams with molds and in-situ growth of polyaniline (PANI). Within the hybrid foam, the CNT/CNF layer provides good electrical conductivity and hydrophilicity, while the highly porous structure still retained after appropriate hot pressing offers numerous pathways for efficient electrolyte ions transportation, and the loaded polyaniline is mainly responsible for the improved electrochemical capacitive properties. A symmetrical all-solid-state SC is assembled using the as-prepared WPUF-derived electrode, which displays superb physical and electrochemical performances, namely, excellent flexibility, high specific capacitance, and great stability at different bending angles. Interestingly, a flexible neat polyurethane membrane can also be easily prepared from WPUF via hot pressing, which is then applied to encapsulate SC to form a novel all-WPUF-based energy wristband to power an electronic watch. This study demonstrates a facile and scalable strategy for the fabrication of high-performance electrodes for wearable electronic devices, using the abundant polymeric wastes as the raw materials.