Impact of Chloride and Bromide Composition in Ionic Liquid/Water Electrolytes on the Electrochemical Performance of Graphene-Based Supercapacitors: A Molecular Dynamics Study

The electrochemical performance of supercapacitors (SCs)
is significantly
influenced by the composition of their electrolytes. In this study,
we investigate the effects of chloride ([Cl]−) and
bromide ([Br]−) anion variations in 1-butyl-3-methylimidazolium
[bmim]+/water mixtures for graphene-based SCs using atomistic
molecular dynamics simulations. We analyze the structural and energetic
profiles of the electrical double layer (EDL), focusing on ion and
water distributions, electrostatic charge profiles, and interaction
energies at charged electrode interfaces. The results reveal that
[Cl]− and [Br]− variations have
a minimal impact on electrostatic charge distributions but play a
crucial role in determining the gravimetric energy density of SCs.
Notably, increasing [Cl–] concentration enhances
the gravimetric energy density by approximately 9% without compromising
electrochemical stability, which is particularly advantageous for
weight-sensitive applications such as portable electronics and electric
vehicles. Additionally, we examined the influence of hydration levels,
showing that higher water content improves the gravimetric efficiency
of the electrolyte. These findings provide valuable insights into
optimizing ionic liquid (IL)/water-based electrolytes for high-performance
SCs.