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Graphene oxide film is made of stacked graphene layers with chemical functionalities, and we report that plasticity in the film can be engineered by strain rate tuning. The deformation behavior and plasticity of such functionalized layered systems is dominated by shear slip between individual layers and interaction between functional groups. Stress-strain behavior and theoretical models suggest that the deformation is strongly strain rate dependent and undergoes brittle to ductile transition with decreasing strain rate.

Solid‐electrolytes (SEs) can provide a pathway to increase energy‐density in lithium metal batteries. However, lithium metal penetration through garnet based LLZO solid electrolytes has been identified as a critical failure process. This phenomenon is related to chemo‐mechanical processes which are difficult to probe. In particular, characterizing the dynamic mechanical deformations that occur in electrode‐SE structures is very challenging. This study reports in situ curvature measurements that are thus designed to probe chemo‐mechanical phenomena that occur during lithium plating. The novel experimental cell configuration created for this work shows that pressure builds up in the Li metal during plating, up until the point where short circuits occur. The resulting data are analyzed with a detailed finite element model (FEM) to quantitatively evaluate stress evolution. The results show that Li metal plating within a surface flaw can produce stress build‐up prior to short‐circuiting. The combined results from both the experiments and the FEM suggest that it is critical to minimize surface defects and flaws during the manufacturing processes.

SiO x negative electrodes for Li-ion batteries enable high energy density while providing better structural integrity compared to pure Si electrodes. The oxygen content has a critical impact on structural changes that occur during electrochemical cycling. In this study, the near-surface structural evolution in SiO x thin films with different compositions (0.3 ≤ x ≤ 2) was probed by various electrochemical techniques and X-ray photoelectron spectroscopy. These results show that all of the SiO x films undergo significant chemical changes during cycling. Even the films with high oxygen content (x = 2) undergo significant restructuring after sufficiently long cycling times. The changes that occur in all films indicate that the near-surface regions of SiO x materials react in ways that effectively make them part of the solid electrolyte interphase (SEI). This also implies that tuning the surface oxygen content of Si-based electrodes can be used to control SEI performance. Hence, the structural changes in SiO x observed in this study may provide useful guidelines for designing passivating layers for improved cycle efficiency.

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Lithium metal penetration through garnet based LLZO solid electrolytes (SEs) have been identified as a critical failure process. At critical current density (CCD), LLZO SE has been known to short-circuiting, and can even result in fracturing of the SE. The combined chemo-mechanical phenomena- which can significantly affect the performance in all solid-state batteries, requires detailed investigation of several related phenomena. Characterizing the dynamical mechanical evolution that occurs in the electrode-SE is challenging. Investigation of the mechanical driving forces of lithium metal penetration through the SE is a particularly important challenge. To probe the chemo-mechanical phenomena that occur during lithium plating, this study reports in-situ curvature measurements that were designed to evaluate the stresses that evolve in LLZO during lithium plating. The experimental configuration created for this work provides data which was analyzed with a detailed Finite Element Model (FEM) to quantitatively evaluate stress evolution in the solid electrolyte. The results show that Li metal plating within a surface flaw can produce stress build-up prior to short-circuiting. The combined results from both the experiments and the FEM suggest that it is critical to minimize surface defects and flaws during manufacturing processes.