Phosphorylated Chitosan‐Based Ionogels for Quasi‐Solid‐State Supercapacitors With Activated Carbon Electrodes

Although liquid electrolytes are widely used in electrochemical energy‐storage devices, they present leakage, safety, and packaging challenges. This work investigates a phosphorylated chitosan/1‐ethyl‐3‐methylimidazolium dicyanamide (PCS/EMIMDCA) ionogel as a fluorine‐free quasi‐solid‐state electrolyte for supercapacitors. The phosphorylated chitosan formed a homogeneous, nonleaking ionogel film up to 80 wt% EMIMDCA. FTIR band shifts were consistent with hydrogen‐bonding and ion‐dipole interactions between EMIMDCA and the phosphorylated chitosan matrix. DSC analysis showed suppression of bulk EMIMDCA crystallization over the investigated temperature range, while the main thermal‐decomposition step began at approximately 220 °C. The optimized PCS:EMIMDCA ionogel achieved an ionic conductivity of 5.3 ± 0.3 mS cm −1 at 30 °C and a full‐cell operating voltage of 1.8 V. When assembled in a symmetric activated carbon (AC//PCS:EMIMDCA//AC) device, it delivered a specific capacitance of 28 F g −1 at 1 A g −1 , a specific energy of 9.6 Wh kg −1 and an average specific power of 0.75 kW kg −1 . In long‐term cycling, the ionogel‐based device retained 76% of its initial capacitance after 10,000 cycles, which represents over twice the stability of the neat EMIMDCA system. These results identify phosphorylated chitosan/EMIMDCA ionogels as durable, fluorine‐free electrolytes based on a bio‐derived polymer host, with improved cycling stability compared with neat EMIMDCA.