Assembly of symmetric supercapacitor based on alginate hydrogel electrolyte and polyaniline modified electrodes

Biopolymer-based hydrogel electrolytes can be described as alternative materials for supercapacitors due to their good ionic conductivity, no liquid leakage, and no toxicity, allowing the construction of flexible devices. This work reports the preparation of alginate gels crosslinked with Ca2+, H+, and a combination of Ca2+ and H+, for use as electrolytes in a symmetric supercapacitor with polyaniline (PANI) films as electrodes. Results indicated that the gel formed with both Ca2+ and H+ showed to be the most appropriate for supercapacitor development for presenting the better electrochemical performance of PANI electrodes, higher values of ionic conductivity and capacitance, also presenting good cycling stability. The symmetrical supercapacitor assembled with the alginate gel and conventional PANI electrodes provided a specific capacitance of 15.08 F g-1 at 0.05 mA cm-2 and exhibited good cycling stability with 92% capacitance retention after 1100 cycles. Three supercapacitor devices fabricated with 3D printing were connected in series and used to power a red LED.