Solid Electrolyte Interfaces (SEI). Perla Balbuena Texas A&M University, Engineering balbuena@tamu.edu   SEI layers are known to be formed on the surface of Li batteries due to side reactions caused mainly by reduction or oxidation of solvents at the surface of anodes and cathodes, although other electrolyte components such as salts may contribute to formation of specific products.1 Depending on the type of electrode and electrolyte, a composite inorganic-organic SEI layer may exert a more or less protective role on the electrode structure.2 During the last two decades, a huge amount of research has been oriented towards characterization of structure and composition of SEI layers, and to the development of electrolyte additives that act as stabilizers. More recently, additional focus has been on determining the SEI dynamical evolution3 during battery cycling and its effect on capacity fading. Desired properties of the SEI layer include the ability to self-heal in response to electrode volume changes during charge/discharge. The incorporation of artificial SEI layers4 as special coatings is an alternative that may work depending on the electrode/electrolyte chemistry. We will review the state-of-the-art of knowledge and will discuss remaining outstanding challenges about electrolyte design, and SEI layer formation and evolution and its role on battery performance for Li-ion and Li-air batteries. (1) Lithium-ion batteries: Solid Electrolyte Interphase; Balbuena, P. B.; Wang, Y. X., Eds.; Imperial College Press: London, 2004. (2) Peled, E.: Lithium Stability and Film Formation in Organic and Inorganic Electrolyte for Lithium Battery Systems. In Lithium Batteries; Gabano, J. P., Ed.; Academic Press, 1983. (3) Wang, F.; Graetz, J.; Moreno, M. S.; Ma, C.; Wu, L. J.; Volkov, V.; Zhu, Y. M.: Chemical Distribution and Bonding of Lithium in Intercalated Graphite: Identification with Optimized Electron Energy Loss Spectroscopy. ACS Nano 2011, 5, 1190-1197. (4) Verma, P.; Novak, P.: Formation of artificial solid electrolyte interphase by grafting for improving Li-ion intercalation and preventing exfoliation of graphite. Carbon 2012, 50, 2599-2614. < return