Adapting Simultaneous in Operando Electrochemical Quartz Crystal Microbalance and Electrochemical Impedance Spectroscopy to Studies of Solid Electrolyte Interface Layer Formation on Amorphous Silicon Anodes

Abstract

Lithium-ion Batteries (LIBs) are the electrochemical energy storage technology of choice for an incredible range of technologies. The application of these batteries has, however, been limited by poor energy density, which is due to the low theoretical energy density of the graphite anodes that are standard in the field. Si has long been targeted as a higher energy density anode material, however uncontrolled electrolyte decomposition on its surface has caused poor cycle life and low columbic efficiencies in Si-containing cells. In this work, a new class of organosilicon (OS) additives were introduced to the Si anode literature and their effect on the first-cycle electrochemistry of model anode surfaces was explored using in operando electrochemical quartz crystal microbalancing (EQCM) and electrochemical impedance spectroscopy (EIS). X-ray photoelectron spectroscopy (XPS) was also used to investigate the differences in composition of solid electrolyte interface (SEI) layers formed in the presence and absence of additive. EQCM-EIS experiments demonstrated an increase in OS-treated cell impedance early in the cycle, which lead to the suppression of early electrolyte decomposition on the model anode surface. XPS revealed that OS-treated cells create thinner SEI layers that were richer in LiF and contained less organic material than cells without OS.