Chitosan-poly(ethylene glycol)-NaClO₄ solid polymer electrolytes for activated carbon and flexible laser-induced...

The growing demand for safe, flexible, and sustainable energy storage systems has increased research into all-solid-state supercapacitors. In this work, NaClO₄-doped chitosan-poly(ethylene glycol) (PEG) solid polymer electrolytes (SPEs) were developed and systematically investigated for use in both rigid and flexible all-solid-state supercapacitors. A series of electrolyte compositions containing 0-50 wt% NaClO₄ (designated CPN0-CPN50) was prepared to study how salt concentration affects the structural, thermal, and electrochemical properties of the electrolyte system. Spectroscopic and structural analyses confirmed strong interactions between the polymer matrix and salt, accompanied by an increase in the amorphous character, which is favorable for ion transport. Thermal studies further indicated composition-dependent thermal behavior and suitable stability over the investigated temperature range. Among the investigated compositions, the electrolyte containing 30 wt% NaClO₄ (CPN30) showed the best performance, exhibiting bulk conductivity of 259.55 ± 19.88 µS cm^-1, with an electrochemical stability window of 2.6 V, and an ionic transference number (0.9988), indicating dominant ionic conduction. The CPN30 electrolyte was integrated into symmetric activated carbon (AC) electrodes and laser-induced graphene (LIG) electrodes. The AC-based device showed a specific capacitance of 19.65 F g^-1 at 1 mV s^-1 from cyclic voltammetry (CV) and 19.01 F g^-1 at the current density of 0.09 A g^-1 from galvanostatic charge-discharge (GCD) analysis. The flexible LIG-based device achieved an areal capacitance of 22.31 mF cm^-2 at 1 mV s^-1 from CV and 19.94 mF cm^-2 at the current density of 0.0225 mA cm^-2 from GCD. Following this, mechanical flexibility tests demonstrated that the LIG-based device retained approximately 95.00% of its capacitance from the bending angle 180° to 90° and 92.56% after 500 bending cycles. In addition, after 3000 cycles, the device retained 87.52% of its initial capacitance, with a coulombic efficiency of 91.42%. These results suggest that NaClO₄-doped chitosan-PEG electrolytes are promising candidates for sustainable, flexible solid-state energy storage applications.