Monitoring Volumetric Changes in Silicon Thin-Film Anodes through In Situ Optical Diffraction Microscopy

Abstract

A high-resolution in situ spectroelectrochemical optical diffraction experiment has been developed to understand the volume expansion/contraction process of amorphous silicon (a-Si) thin-film anodes. Electrodes consisting of 1D transmissive gratings of silicon have been produced through photolithographic methods. After glovebox assembly in a home-built Teflon cell, monitoring of the diffraction efficiency of these gratings during the lithiation/delithiation process is performed using an optical microscope equipped with a Bertrand lens. When the diffraction efficiency along with optical constants obtained from in situ spectroscopic ellipsometry is utilized, volume changes of the active materials can be deduced. Unlike transmission electron microscopy and atomic force microscopy characterization methods of observing silicon's volume expansion, this experiment allows for real-time monitoring of the volume change at charge/discharge cycles greater than just the first few along with an experimental environment that directly mimics that of a real battery. This technique shows promising results that provide needed insight into understanding the lithium alloying reaction and subsequent induced capacity fade during the cycling of alloying anodes in lithium-ion batteries.

In situ and Operando Tracking of Microstructure and Volume Evolution of Silicon Electrodes by using Synchrotron X‐ray Imaging

“…Note that this extended expansionp eriod was previously discovered when monitoring volumetric changes in Si thin film. [26] As imilar phenomenon, albeit with an early termination of the particle'sv olumee xpansion, was reportedf or Si 0.64 Sn 0.36 alloy [27] and Sn electrodes. [28] Despite these previous reports, the asynchronization of particles' volume change with the (dis)charging state of the electrode has been rarely investigated to date, especially quantitatively.I nF igure 4a and 4b,t he diameter developmento fp article P1 (Figure 2c)a nd diameter/ volumev ariation of another two particles (denoteda sP2 and P3;s ee Figure 4a and FigureS3) during lithiation and delithiation are shown for comparison.…”

“…124 minutes). The time/capacity between the start of delithiation and reaching the maximum particle diameter is thereafter named “expansion prolongation” period and is highlighted by the blue arrow in Figure c. We note that the same extended expansion phenomenon during delithiation was reported before but without detailed explanation . Further exploration and interpretation of this phenomenon are presented below.…”

“…Note that this extended expansion period was previously discovered when monitoring volumetric changes in Si thin film . A similar phenomenon, albeit with an early termination of the particle's volume expansion, was reported for Si 0.64 Sn 0.36 alloy and Sn electrodes .…”

Bioinspired Controllable Electro‐Chemomechanical Coloration Films

“…In the SE models, the a‐Si layer is modeled as a Brendel oscillator, while the optical constants of the copper substrate layer are found in the Palik optical handbook at delithiated state. For the lithiated state, the surface of coloration film is complicated in its components and has a rough ultrathin SEI layer, as displayed in Figure b. To simplify the physical model, the effective medium approximation (EMA) layer is added up to the Li x Si layer (Brendel oscillator), and the a‐Si layer is ignored because of the uniform Li intercalation in our experiments.…”

Local Substrate Heterogeneity Influences Electrochemical Activity of TEM Grid-Supported Battery Particles

“…The optical signal is insensitive to electrical double layer charging but sensitive to redox changes of elements in the particle (e.g., W 6+ /W 5+ in WO 3 ). Widefield optical imaging has been used to characterize Li-ion insertion in electrochromic WO 3 and MoO 3 thin films Stevenson, 2003, 2005a,b;Kondrachova et al, 2009) and battery materials at the ensembleand single microparticle-levels (Harris et al, 2010;Love et al, 2015;Duay et al, 2016;Wood et al, 2016;Sanchez et al, 2020), but the aforementioned studies have not linked electrochemical and composition/structural analysis at the single particle-levels. This widefield approach enables one-to-one electrochemical-tostructural characterization of tens to hundreds of particles in a single experiment, limited by the coverage of single particles on the TEM substrate.…”