Adsorption of ions at the solid-liquid interface is central to many natural processes and applications such as corrosion of metals, electrochemical energy storage, and swelling of clays. In these processes, the composition of electrolyte has a profound influence on the structure, dynamics and energetics of the ions and water at interface. Atomistic simulations are practical to properly explore cation-specific effects and concentration-dependence at molecular level. We perform molecular dynamics (MD) simulations to examine the ion adsorption, hydration and electric double layer structures, and ion transport behavior in aqueous electrolytes (Cs+, Li+, and Ca+2 ions) confined between two negatively charged mica surfaces. Our simulation results show that Cs+ ions have the most prominent screening effect at the surface, indicating a stronger ion adsorption compared to Li+ and Ca+2 ions at the same concentration. Interestingly, the number of adsorbed Cs+ ions exceeds the surface charge of mica. This refers to a phenomenon called as “overscreening”. As a result, the surface becomes positively charged, and the diffuse layer of EDL becomes co-ion dominated. However, this is not the case for Li+ and Ca+2 which they attach less strongly to the surface and undercharge the mica. These ion adsorption directly affects the water structures. Although there are less Li+ ions at the surface compared to Cs+, more water molecules come near to the surface from the center of the channel for Li case. Water molecules can go through between adsorbed Li+ layer and the surface, strongly hydrating Li+ ions whereas this is not possible for Cs+. These indicate that hydration is the driving force in Li solution while surface forces are dominant in Cs case. By assessing the competitive behavior of charged species at the surface, the adsorption coverage is quantified as a function of ion concentration. Cs+ coverage significantly increase with the increase of concentration while a linear but less prominent increase is obtained for Li+ adsorption. On the other hand, increased ion concentration shows a negligible influence on the Ca+2 coverage. MD simulation results highlighting the ion adsorption as a function of ion type and concentration is critical to understand the interfacial thermodynamics directly from high resolution atomic force microscopy imaging.