High performing all-solid electrochemical capacitor using chitosan/poly(acrylamide-co-diallyldimethylammonium chloride) as anion conducting membranes

The aim of the present work is to demonstrate a novel alkaline anion-exchange membrane composed of chitosan (CS) and poly (acrylamid-co-diallyldimethylammonium chloride) (PAADDA) for electrical double layer capacitors (EDLCs). The CS-PAADDA-OH^- membranes were prepared through a combined thermal and chemical cross-linking strategy and their physical-chemical properties were investigated. As a notable example, when the mass fraction of PAADDA was about 33%, the CS-PAADDA-OH^- membrane exhibits excellent OH⁻ conductivity, reaching high as 0.0151 S cm⁻¹, while its water uptake is only about 32.23%. Such membrane also showed optimal mechanical property and excellent thermal stability, due to the compact and dense network. Moreover, all the testing membranes showed high oxidative stability in 30% H₂O₂ solution, and a robust alkaline stability in 8 M KOH at 60 °C for 320 h of evaluation. The resultant EDLC device demonstrated a voltage window at about 1.2 V, sustaining a cycle-life over 2000 cycles. Even when the scan rate is up to 5 V s⁻¹, the device still maintained excellent rate capability. This study provides feasibility of transforming bulky liquid devices to safer and solid thin devices.