Advanced eco-conscious amylaceous biopolymer electrolytes functionalized with potassium iodide for high-performance flexible potassium-ion batteries

Solid biopolymer electrolytes (SBEs) based on cornstarch and potassium iodide (KI) have been developed via solution casting, demonstrating enhanced safety and flexibility for potassiumion batteries (KIBs). X-ray diffraction has been confirmed KI reduced semicrystallinity, while Fourier transform infra-red spectroscopy (FTIR) revealed cation interactions with C‒O band, yielding 75.19 % free ions. Moreover, 70/30 (cornstarch/KI) composition achieved optimal ionic conductivity (2.50 × 10⁻⁴ S/cm at 303K) with minimal activation energy (0.13 eV). Theoretical modelling validated the Overlapping Large Polaron Tunnelling and Small Polaron Hopping models accurately describe ion conduction, specifically at mid and high frequency ranges. Dielectric analysis showed an exceptional dielectric constant of 7.86 × 10⁶ at 42 Hz. A negative dielectric constant of −273.897 emerges at 1 MHz due to the prevailing inductive response in this frequency range. The SBE exhibited a high ion transference number (0.98) and ultrafast relaxation (1.01 μs). A flexible KIB delivered an open-circuit voltage of 1.085 V, showcasing its potential for next-generation energy storage.