This work describes the effect of potential and temperature on the grapheneionic liquid (EMImBF4) interfacial structure and properties with the focus on a novel phenomenon of ionic saturation. We apply classical molecular dynamics simulations to reproduce well-known phenomena of overscreening, mono -layer formation, and temperature-induced smearing of the interfacial structure. Using quantum density functional theory calculations, we show how quantum capacitance dampens the influence of temperature and improves the agreement with the experimental data. Using a bilayer model, we study characteristic features of capacitance-potential dependence and relate them to the changes in interfacial structure. These insights are of fundamental and practical importance for the application of similar interfaces in electrochemical energy storage and transformation devices such as capacitors and actuators. (C) 2022 The Authors. Published by Elsevier B.V.