Carbon nanomaterials, particularly graphene nanoplatelets (GNPs), have garnered significant attention as electrode materials for supercapacitors due to their exceptional properties, including high surface area, excellent electrical conductivity, chemical stability, and low toxicity. Their versatility in structural and chemical modifications further enhances their suitability for advanced energy storage applications. In this study, we propose a novel device architecture based on a GNP/polyethylene (PE) membrane/copper stack, where the PE membrane is impregnated with the ionic liquid N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis-(trifluoromethylsulfonyl)-imide ([DEME][TFSI]), forming a stable and efficient electrochemical cell. We investigate the charge accumulation mechanisms in ionic capacitors employing GNP electrodes under varying bias conditions. Furthermore, we analyze the relationship between the operating conditions particularly the applied voltage and the resulting capacitance, providing insights into the optimization of these devices for improved energy and power density. Our findings highlight GNP-based ionic capacitors position them as highly promising candidates for next-generation energy storage solutions and advanced electronic applications. © 2025 Elsevier B.V., All rights reserved.