Unveiling the origin of early-stage defect formation in Si electrodes

Si is a very promising anode material for future lithium-ion batteries (LIBs) due to its high Li-accommodation capability. The theoretical specific capacity of Si is up to 3579 mAh g-1, 9 times more than carbon-based materials (372 mAh g-1), such as graphite. Unfortunately, this high storage capacity is accompanied with a 3-fold volume change, which could cause mechanical fracture to the Si matrix. Intensive experimental and theoretical efforts have been devoted to understanding the structural deformation of Si electrodes. However, these experiments or simulations are only based on observations in a later stage of deformation, like volume expansion or cracks, without unveiling the early-stage nature.In this work, we applied multiple operando tools to study the origin of early-stage defects (deformations) in Si electrodes. Firstly, by performing operando full-field diffraction x-ray microscopy, early-stage defects (lattice-tilts) in Si electrodes were studied of which the origin can be related to a heterogeneous lithiation. This lithiation heterogeneity was then further correlated to the inhomogeneities in the dual-layer solid-electrolyte interphase (SEI), which was identified by operando atomic force microscopy, electrochemical strain microscopy and sputter-etched x-ray photoelectron spectroscopy. Our study bridges observations across the multi-level interfaces (Si/LixSi/inner-SEI/outer-SEI), offering novel insights into the structural stability of Si-based LIBs.

C. Chen, T. Zhou, D. L. Danilov, L. Gao, S. Benning, N. Schön, S. Tardif, H. Simons, F. Hausen, T. U. Schülli, R.-A. Eichel, P. H. L. Notten, Nat. Commun. 2020, 11, 3283 (1-10).