Sulfonated White-Graphene for High-Performance Gel Polymer Electrolytes: The Interplay between Ion Conductivity and Rheology.

Research into flexible solid-state supercapacitors for wearable electronics focuses on achieving high performance and safety. Gel polymer electrolytes (GPEs) are preferred over fully solid-state electrolytes due to their better ionic conductivity while addressing safety concerns associated with liquid electrolytes. This study aims to enhance high-performance gel polymer electrolytes (HP-GPEs) by improving the ion transfer rate of polyvinyl alcohol (PVA) with sulfonated hexagonal boron nitride (known as white-graphene) and exploring how rheology influences ion-conduction within HP-GPEs. The systematic analysis of GPEs highlights the dominant role of the loss factor in quasi-solid GPEs. With less energy dissipation in the polymeric structure, ion movement occurs along an optimized pathway, as reflected in the calculated values of the diffusion coefficient and ion mobility from impedance analysis. Physico-electro-chemical characterizations of the HP-GPEs revealed that the 3D network of 2D nanosheets and crystallites formed a more uniform and reduced pore size (decreasing from ≈7 µm to ≈221 nm), increased ion conduction by 6-fold (70.7 mS cm), and led to an increment of ≈35% in specific capacitance with an impressive 96% retention after 10 000 cycles. These findings underscore the importance of engineering the rheological and structural properties in hydrogels as promising electrolytes for high-performance energy storage devices.