"Solid Electrolyte Interphase on Native Oxide-Terminated Silicon Anodes for Li-Ion Batteries"

Chuntian Cao: Iwnetim Iwnetu Abate, Eric Sivonxay, Badri Shyam, Chunjing Jia, Brian Moritz, Thomas P. Devereaux, Kristin A. Persson, Hans-Georg Steinrück, and Michael F. Toney; Joule, 03/20/19.

Additional Authors: Iwnetim Iwnetu Abate, Eric Sivonxay, Badri Shyam, Chunjing Jia, Brian Moritz, Thomas P. Devereaux, Kristin A. Persson, Hans-Georg Steinrück, and Michael F. Toney

Abstract:

Context & Scale:

Despite the electronic revolution initiated by lithium-ion batteries (LIBs) three decades ago, one aspect of these energy storage devices still puzzles researchers. This is the solid electrolyte interphase (SEI) that forms on electrodes because LIBs operate outside the electrolyte stability window and can effectively passivate the electrode. Experimentally, the SEI is challenging to study with the desired atomic resolution as it is buried at the electrolyte-electrode interface.
In this article, we provide fresh insights into the nature and transport properties of the SEI, via a multi-property combined experimental and simulation approach utilizing well-defined model systems. We unraveled the structure and composition, as well as the formation mechanism of the SEI on silicon anodes. Our findings are discussed with regard to understanding possible SEIinduced bottlenecks in LIBs and the relevance for their optimization.

Summary:

To shed light on the formation process and structure of the solid electrolyte interphase (SEI) layer on native oxide-terminated silicon wafer anodes from a carbonate-based electrolyte (LP30), we combined in situ synchrotron X-ray reflectivity, linear sweep voltammetry, ex situ X-ray photoelectron spectroscopy, and first principles calculations from the Materials Project. We present in situ sub-nanometer resolution structural insights and compositional information of the SEI, as well as predicted equilibrium phase stability. Combining these findings, we observe two well-defined inorganic SEI layers next to the Si anode—a bottom-SEI layer (adjacent to the electrode) formed via the lithiation of the native oxide, and a top-SEI layer mainly consisting of the electrolyte decomposition product LiF. Our study provides novel mechanistic insights into the SEI growth process on Si, and we discuss several important implications regarding ion and electron transport through the SEI layer.