Self‐Healable and Eco‐Friendly Hydrogels for Flexible Supercapacitors

One limitation of wearable electronics, and at the same time a challenge, is the lack of energy storage devices with multiple functionalities produced using clean and environmental‐friendly strategies. Here, a multifunctional conductive hydrogel containing poly(3,4‐ethylenedioxythiophene) (PEDOT) and alginate is fabricated, to be used as electrodes in supercapacitors, by applying water‐mediated self‐assembly and polymerization processes at room temperature. The interpenetration of both polymers allows the combination of flexibility and self‐healing properties within the same hydrogel together with the intrinsic biocompatibility and sustainability of such materials. Initially, PEDOT:polystyrene sulfonate and alginate aqueous solutions are mixed in two different proportions (1:1 and 1:3) and ionically crosslinked with CaCl 2 . Subsequently, re‐interpenetration of poly(hydroxymethyl‐3,4‐ethylenedioxythiophene) by anodic polymerization in CaCl 2 aqueous solution is achieved. Re‐interpenetrated 1:3 PEDOT/alginate hydrogels show excellent capacitance values (35 mF cm −2 ) and good capacitance retention. In addition, the electrochemical properties are not significantly changed after many cutting/self‐healing cycles as observed by cyclic voltammetry. Therefore, this sustainably produced hydrogel shows promising properties for use in wearable energy storage devices.