A Study of Bulk and Interfacial Properties of Li Based Electrolytes Utilized in Lithium Ion Batteries

Li-ion batteries are very important energy storage devices for long term and steady energy supply. The electrolyte in these devices contains a Li-salt dissolved in an organic solvent. The choice of the salt and solvent could dramatically improve the performance of Li-ion batteries, and an active area of research in this field is to find new salts and less viscous and less flammable solvents. This poster will present a study of several Li-salts (LiPF6, LiTFSI, LiDFOB and LiBOB) dissolved in solvents commonly utilized for Li-ion batteries applications. The dynamic properties such as diffusion coefficients and the residence time of Li near carbonate groups, as well as the structural properties such as radial distribution functions, coordination numbers, density profiles from electrode will be analyzed as a function of distance from electrode, electrode potential, salt structure and utilized solvent (EC, EC/DMC, PC).  We show that due to a strong binding of Li to carbonate solvent there is a weak dependence of the interfacial Li⁺ concentration on applied potential. Retention of Li⁺ near positive electrode is possible up to +2V. In contrast the anion is quickly repealed from the negative surface. Addition of LiHBOB or LiBOB salts in the system can diminish the PF₆ anion concentration in EDL however these additional anions do not replace the PF₆ completely in the EDL.