On the influence of polarization effects in predicting the interfacial structure and capacitance of graphene-like electrodes in ionic liquids

The electric double layer (C_D) and electrode quantum (C_Q) capacitances of graphene-based supercapacitors are investigated using a combined molecular dynamics and density functional theory approach. In particular, we compare an approach that includes electronic polarization to one that is polarization-free by evaluating both C_D and C_Q using [EMIM][BF₄] ionic liquid as a model electrolyte. Our results indicate that the inclusion of polarization effects can yield higher C_D values - in this study by up to 40% around ±2 V - which we attribute primarily to the presence of charge smearing at the electrode-electrolyte interface. On the other hand, we find that the polarization-induced distortion of the electronic structure of graphene does not noticeably alter the predicted C_Q. Our analysis suggests that an accurate description of the spatial charge distribution at the graphene interface due to polarization is necessary to improve our predictive capabilities, though more notably for C_D. However, the conventional polarization-free approximation can serve as an efficient tool to study trends associated with both the C_Q and C_D at the interface of various graphene-like materials.