Integrated paper electrodes derived from cotton stalks for high-performance flexible supercapacitors

With the rapid development of flexible electronics, new opportunities are opening up for paper-based electrodes. Herein, an integrated paper electrode consisting of homogeneously mixed cellulose fibers, activated carbon (AC), and carbon black is fabricated using cotton stalks as the raw material. Assembled from two such electrodes, the flexible supercapacitor exhibits high energy density, high power density, and outstanding cyclability. Remarkably, the thickness and AC mass loading of the paper electrode can be easily scaled up to commercial levels (610 µm and 9.8 mg cm−2), while still delivering great performances. Moreover, it is demonstrated that the replacement of AC with Ni-Co layered double hydroxide or Fe2O3 can result in paper-based asymmetric supercapacitor with extremely high energy density (331 μW h cm−2 and 10.3 mW h cm−3), substantially outperforming conventional paper-based supercapacitors. The fabrication methodology of integrated paper electrodes in this report manifests great potential, offering a new vision for flexible energy storage.