(Invited) Ultrathin Polymer Electrode Coatings to Stabilize Electrochemical Interfaces in Lithium-Ion Batteries

Abstract

Safety and performance of Li-ion batteries lie at the electrochemical interfaces. Local surface chemistry and electrochemistry at the battery negative electrode will dictate whether stable intercalation or unstable deposition processes are favored. This talk will present the environmental, electrochemical and chemical effects, namely temperature, current density and negative electrode surface coatings, have on the nucleation, growth and morphology of electrodeposited lithium. We use initiated chemical vapor deposition (iCVD) to generate ultrathin polymer coatings with thickness control at the nanoscale [1], even on complex three-dimensional (3D) substrates [2] such as carbonaceous negative composite electrodes. The siloxane-based polymers most commonly generated by iCVD contain ether-like functionalities that support the solvation and transport of Li+ salts, such that they are readily transformed into Li-ion conductors [3]. Polymer-modified electrodes are assembled into Li-ion coin cells containing liquid electrolytes, in which we examine such properties as specific power, coulombic efficiency, cycle life, and tolerance to overcharge/overdischarge conditions. In-situ optical microscopy observation of galvanostatic plating and stripping experiments provides valuable understanding of morphology, growth behavior, and propensity to form internal short circuits. These observations are then coupled with cell impedance changes detected through electrochemical impedance spectroscopy to develop advanced diagnostic and fault detection techniques. Tenhaeff, W.E.; Gleason, K.K. Func. Mater. 2010, 18, 979.Sassin, M.B.; Long, J.W.; Wallace, J.M.; Rolison, D.R. Horizons 2015, 2, 502.Reeja-Jayan, N. Chen, J. Lau, J. A. Kattirtzi, P. Moni, A. Liu, I. G. Miller, R. Kayser, A. P. Williard, B. Dunn, and K. Gleason, Macromolecules 48, 5222 (2015).