3.3 Cellulose and conducting polymers for large-scale paper supercapacitors on demand

Driving sustainability and the increasing demand for electrical energy hand in hand requires both the utilization of abundant green resources and the use of efficient large-scale manufacturing techniques. As regards abundance, forest derived materials and organic conducting polymers are powerful candidates. In terms manufacturing, roll-to-roll, printing techniques are identified as key technological processes. In this work we combine cellulose, the conducting polymer PEDOT:PSS, and carbon derivatives for printable supercapacitor electrodes. Cellulose provides a mesoscopic mesh for the organization of the active ingredients while PEDOT:PSS acts as a mixed ion-electron conducting glue, which physically binds activated carbon particles together, facilitating swift transport of both electrons and ions. We discovered that a surprisingly small amount (10%) of PEDOT:PSS is needed to achieve an optimal performance. Furthermore, we report on a flexible ‘on demand’ printing design for these supercapacitors that allows the production of both individual devices or the combination of devices in parallel and in series to increase the capacitance and voltage, respectively. The individual device showed impressive capacity up to 10 F while increasing the area with the large parallel device increased the capacitance to a record 127.8 F (332.8 mF/cm2). A 5 V supercapacitor was produced by arranging 4 supercapacitors in series. This work demonstrates the possibilities of  ‘on-demand’ printable, efficient, and mechanically robust energy storage devices from cellulose and PEDOT:PSS-carbon.