Résumé
Water-in-salts are a new family of electrolytes that may allow the development of aqueous Li-ion batteries. They have a structure which is reminiscent of the one of ionic liquids, and they are characterized by a large concentration of ionic species. In thiswork we study their transport properties and how they evolve with concentration byusing molecular dynamics simulations. We first focus on the choice of the force field.By comparing the simulated viscosities and self diffusion coefficients with experimentalmeasurements, we select a set of parameters that reproduces well the transport proper-ties. We then use the selected force field to study in detail the variations of the self andcollective diffusivities of all the species as well as the transport number of the lithiumion. We show that correlation between ions and water play an important role over thewhole concentration range. In the water-in-salt regime, the anions form a percolatingnetwork which reduces the cation-anion correlations and leads to rather large valuesfor the transport number compared to other standard electrolytes