Temperature dependence of electric double-layer structure and electrochemical properties in graphene supercapacitors with [emim][BF₄] electrolyte: a molecular dynamics study

Abstract

This work presents an investigation into the impact of temperature on the electrochemical properties of supercapacitors using classical molecular dynamics simulations. Devices composed of graphene electrodes and [emim][BF₄] electrolyte were analyzed over a temperature range from 300 K to 600 K. The results indicate that, although ionic mobility increases with temperature, the electric double layer (EDL) structure remains stable, leading to capacitance variations below 13 %. The electrode–electrolyte interaction energy remains virtually unchanged across the thermal range, preserving device efficiency at elevated temperatures. Estimated energy densities reach up to 8 J/g at 3 V and 600 K, highlighting the potential of graphene-based supercapacitors for applications in extreme thermal environments. The methodology employed incorporates temperature-dependent densities obtained from NPT simulations of the pure ionic liquid to realistically model confined systems—an approach still rarely explored in the literature. Additionally, the careful treatment of the potential of zero charge (PZC) under asymmetric electrolyte conditions enables a more accurate description of interfacial electrostatics.