Spatial Structure of Electrical Diffuse Layers in Highly Concentrated Electrolytes: A Modified Poisson–Nernst–Planck Approach

Abstract

Studies of room-temperature ionic liquids showed that electrical diffuse layers in these highly concentrated electrolytes may exhibit spatially extended nonmonotonic (oscillatory) and monotonic decays. These unconventional properties are fundamentally different from traditional (dilute) electrolytes and demonstrate the limited mechanistic understanding of highly concentrated electrolytes. Moreover, electrolyte behavior placed in close proximity of two charged surfaces becomes even more unclear due to the possible overlap between diffuse layers. The latter is important as many applications require confinement into narrow spaces, e.g., energy and lubrication related applications. To advance the understanding of electrical diffuse layers in highly concentrated electrolytes (and ionic liquids) we use a semiphenomenological modified Poisson–Nernst–Planck equation and regulate weak dilutions. Using spatial dynamics methods and numerical computations, we analyze distinct diffuse layer characteristics (nonmonoton...