Synthesis of PVA/corn starch hydrogel polymer electrolytes for supercapacitors.

Supercapacitors have garnered attention from researchers due to their high power density, fast charge–discharge, and excellent cycle life as an alternative to batteries. However, they have low energy density relative to batteries. Two approaches can be taken to increase the energy density of supercapacitors (i) increase the capacitance of the electrode materials or (ii) increase the electrochemical potential window of the electrolyte. In this research, we formulated a novel hydrogel polymer electrolyte with a wide electrochemical potential window using poly (vinyl alcohol) (PVA)/corn starch/sulfuric acid (H₂SO₄) formed via glutaraldehyde crosslinking by forming acetal bridges between hydroxyl groups of the polymers. Stronger hydrogen bonding and abundance of electron donor atoms due to the addition of corn starch led to the formation of an ion transport path that allowed ions to move with ease, resulting in a hydrogel polymer electrolyte with exceptional ionic conductivity of 7.49 × 10⁻² S cm⁻¹. Moreover, the wider electrochemical potential window is achieved due to the stronger hydrogen bonding formed between the polymers and water molecules, preventing hydrogen evolution. When an electric double layer capacitor (EDLC) is assembled using the hydrogel and two symmetrical activated carbon-based electrodes, it achieved an outstanding energy density of 11 Wh kg⁻¹, maximum power density of 1433 W kg⁻¹, and negligible capacity loss over 4000 cycles. This study also highlights the effect of the addition of corn starch on the ionic conductivity and properties of hydrogel polymer electrolytes. [ABSTRACT FROM AUTHOR]