Supporting information for this article is given via a link at the end of the document. Safer-by-design and sustainable energy storage devices are envisioned as among the required 2.0 solutions to satisfy the fastgrowing energy demands. Responding to this evolution cannot be freed from a global and synergetic approach to design the requisite electrolytes taking into account the toxicity, the eco-compatibility and the cost of their constituents. An unprecedented strategy was performed targeting low temperature applications, a non-toxic and cost-efficient eutectic system LiNO3 in water with 1,3-propylene glycol as co-solvent was concomitantly selected to design a ternary electrolyte with a wide liquid range. By using this electrolyte in an electrostatic double-layer capacitor (EDLC), the operating voltage of the device reaches an optimum of 2.0 V at-40 °C over more than 100 h of floating. Moreover, after being set up at 20 °C, the temperature resilience of the capacitance is near total, demonstrating thus a promising feature related to the suitable thermal and electrochemical behaviours of the tested EDLC devices.