Evaluation of Structural and Electrochemical Properties of Supercapacitors with Graphene Electrodes and Hydrated Pure or Mixed [bmim]-Based Ionic Liquids via Molecular Dynamics.

Abstract

This study investigates the effect of anion composition on the performance of supercapacitors (SCs) using hydrated ionic liquids and graphene electrodes, focusing on comparing pure and mixed electrolytes. Systems containing [bmim] paired with NO₃ ^-, ClO₄ ^-, and Br^- were evaluated to assess their impact on electric double layer (EDL) formation and electrochemical behavior. Molecular dynamics (MD) simulations were performed under varying surface polarization, focusing on interaction energies, species distribution, capacitance, and projected energy density. Capacitance values ranged from 2.30 to 2.55 μF/cm², while energy densities varied between 5.03 and 5.58 J/g, depending on electrolyte composition. The results show that small, mobile anions like Br^- promote more compact EDLs and higher capacitance, even with weak electrode interactions. NO₃ ^- contributes to interfacial organization through hydrogen bonding with water. Mixed anion systems demonstrated competitive performance, with the best results obtained by combining high ion mobility and structural organization. This suggests that hybrid electrolytes are a promising strategy for optimizing energy storage in ionic liquid-based SCs.