Impact of dual-layer solid-electrolyte interphase inhomogeneities on early-stage defect formation in Si electrodes

Chunguang Chen,Dmitri L Danilov,Lu Gao,Florian Hausen,Samuel Tardif,R.-A Eichel,Tao Zhou,Nino Schön,Peter H L Notten,Svenja Benning,Tobias U Schülli,Hugh Simons

doi:10.1038/s41467-020-17104-9

Abstract

While intensive efforts have been devoted to studying the nature of the solid-electrolyte interphase (SEI), little attention has been paid to understanding its role in the mechanical failures of electrodes. Here we unveil the impact of SEI inhomogeneities on early-stage defect formation in Si electrodes. Buried under the SEI, these early-stage defects are inaccessible by most surface-probing techniques. With operando full field diffraction X-ray microscopy, we observe the formation of these defects in real time and connect their origin to a heterogeneous degree of lithiation. This heterogeneous lithiation is further correlated to inhomogeneities in topography and lithium-ion mobility in both the inner- and outer-SEI, thanks to a combination of operando atomic force microscopy, electrochemical strain microscopy and sputter-etched X-ray photoelectron spectroscopy. Our multi-modal study bridges observations across the multi-level interfaces (Si/LixSi/inner-SEI/outer-SEI), thus offering novel insights into the impact of SEI homogeneities on the structural stability of Si-based lithium-ion batteries.

Highlights

While intensive efforts have been devoted to studying the nature of the solid-electrolyte interphase (SEI), little attention has been paid to understanding its role in the mechanical failures of electrodes
Local stress is often underestimated and, in particular, the early stage of defect formation has mostly been neglected. These experiments were performed in the presence of a liquid electrolyte, with the solid-electrolyte interphase (SEI) layer significantly hindering the investigations of mechanical failure mechanisms in the underlying Si electrodes
We study the evolution of structural deformation in Si electrodes, using a multimodal approach consisting of full-field diffraction X-ray microscopy (FFDXM), atomic force microscopy (AFM), electrochemical strain microscopy (ESM), and sputteretched X-ray photoelectron spectroscopy (XPS)

Summary

Introduction

While intensive efforts have been devoted to studying the nature of the solid-electrolyte interphase (SEI), little attention has been paid to understanding its role in the mechanical failures of electrodes. Si-based nanoparticle/thin-film anodes are shown to have a size- and thickness-dependent fracture behavior upon (de)lithiation[17,18] The majority of these experiments were performed without any spatial resolution, yielding only averaged information on the evolution of structural deformation[10,11,12,13,14,15,16,17,18]. Local stress is often underestimated and, in particular, the early stage of defect formation has mostly been neglected These experiments were performed in the presence of a liquid electrolyte, with the solid-electrolyte interphase (SEI) layer significantly hindering the investigations of mechanical failure mechanisms in the underlying Si electrodes. Spatially resolved studies that offer a better understanding of the correlation between the SEI and its impact on the structural stability of the underlying electrode are in urgent demand

Methods

Results

Conclusion