Doped photo-crosslinked polyesteramide hydrogels as solid electrolytes for supercapacitors†
High-performance hydrogels play a crucial role as solid electrolytes for flexible electrochemical supercapacitors (ESCs). More specifically, all solid-state ESCs based on renewable, biodegradable and/or biocompatible hydrogels doped with inorganic salts as electrolytes are attractive not only because of their contribution to reducing resource consumption and/or the generation of electronic garbage, but also due to their potential applicability in the biomedical field. Here, computer simulations have been combined with experimental measurements to probe the outstanding capability as solid electrolytes of photo-crosslinked unsaturated polyesteramide hydrogels containing phenylalanine, butenediol and fumarate, and doped with NaCl (UPEA-Phe/NaCl). Atomistic molecular dynamics simulations have shown the influence of the hydrogel pore structure in the migration of Na+ and Cl− ions, suggesting that UPEA-Phe/NaCl hydrogels prepared without completing the photo-crosslinking reaction will exhibit better behavior as solid electrolytes. Theoretical predictions have been confirmed by potentiodynamic and galvanostatic studies on ESCs fabricated using poly(3,4-ethylenedioxythiophene) electrodes and UPEA-Phe/NaCl hydrogels, which were obtained using different times of exposure to UV radiation (i.e. 4 and 8 h for incomplete and complete photo-crosslinking reaction). Moreover, the behavior as a solid electrolyte of the UPEA-Phe/NaCl hydrogel prepared using a photo-polymerization time of 4 h has been found to be significantly superior to those exhibited by different polypeptide and polysaccharide hydrogels, which were analyzed using ESCs with identical electrodes and experimental conditions.