Deciphering KI-Infused Dual-Polysaccharide-Derived Flexible Electrolyte Films for Nonfaradaic Energy Storage

Abstract The development of potassium-ion-based solid polymer electrolytes remains largely underexplored due to their poor environmental degradability, insufficient ionic conductivity, and inadequate mechanical flexibility for energy-storage applications. To address these gaps, a dual-biopolymer-based electrolyte was developed by combining two natural polysaccharides, Konjac glucomannan (KGM) and Guar gum (GG), with potassium iodide (KI) using a simple in situ gelation method, enabling the formation of hybrid flexible electrolyte films (HFEFs). Structural, morphological, and electrochemical analyses confirm the improved polysaccharide–salt interactions and formation of efficient ion transport pathways within the hybrid matrix. The optimized composition containing 81 wt% of KI (HFEFKI-81) exhibits a maximum ionic conductivity of 2.26 × 10–3 S cm–1 at room temperature, along with an electrochemical stability window of 1.3 V. A supercapacitor was devised by assembling HFEFKI-81 as a solid electrolyte supported by graphite electrodes that demonstrated a specific capacitance (Csp) of 27.6 F g–1 at a current density of 0.1 A g–1, with an excellent cycling stability retaining 77.2% of its specific capacitance over 5000 cycles at a current density of 0.5 A g–1. The device provides an energy density of 2.6 Wh kg–1 and power density of 41.3 W kg–1 at 0.1 A g–1, confirming its suitability for nonfaradaic energy-storage applications.