Hydrogen Bond Interpenetrated Agarose/PVA Network: A Highly Ionic Conductive and Flame-Retardant Gel Polymer Electrolyte

The gel polymer electrolyte (GPE) is the key to assembling high-performance solid-state supercapacitors (SSCs). The commercial poly(vinyl alcohol) (PVA) GPE has developed a reputation due to low ionic conductivity endowed by its high crystallinity and poor water retention capacity. In this work, density functional theory (DFT) calculations first revealed that the high crystallinity of PVA can be greatly disrupted by forming hydrogen bonds with natural agarose macromolecules. The hydrogen bond interpenetrated three-dimensional agarose/PVA network offers high water retention and large amounts of channels for movement of Li⁺ on hydroxyl oxygen atoms. So, an optimized formation of the Li-O coordinate bond (g_Li-O(r) = 8.78) and improved diffusion coefficient of Li⁺ (D_Li⁺) (71 × 10^-6 cm² s^-1) were obtained in the agarose/PVA model. When assembled into SSCs, agarose/PVA-GPE with 2 M LiOAc (AP-GPE) exhibits an outstanding specific capacitance (697.22 mF cm^-2 at 5 mA cm^-2). The high water retention of agarose and large amounts of -OH groups in the agarose macromolecular can generate H₂O by dehydration reaction, reducing the flammability of PVA and greatly enhancing the safety of SSCs.