Volume Changes of Graphite Anodes Revisited: A Combined <i>Operando</i> X‑ray Diffraction and <i>In Situ</i> Pressure Analysis Study

Lithium intercalation into graphite is one of the electrochemically best studied solid-state reactions, and its application in lithium-ion batteries was a pioneering step in the development of advanced electrochemical storage devices. Therefore, one might expect that virtually any aspect of this important reaction has been examined both qualitatively and quantitatively. All the more, it is surprising that there are only a few experimental studies on the volume expansion of graphite, especially under cycling conditions. To the best of our knowledge, there exists no comprehensive set of structural data as a function of lithium content. Here, we present this missing information using combined results from electrochemical testing and <i>operando</i> X-ray diffraction. The changes in lattice parameters and unit cell volume are examined and related to the different intercalation stages and phase transition regimes. A total volume expansion (from space-group-independent evaluation) of 13.2% is observed when C₆ is fully lithiated to a composition of LiC₆, of which approximately 5.9% occur in the early dilute stages. The remaining expansion of approximately 7.3% is due to transition from stage 2 to stage 1. These findings are corroborated by <i>in situ</i> pressure measurements on prelithiated Li₄Ti₅O₁₂/graphite cells. Collectively, our data provide valuable information about one of the most important electrode materials for lithium-ion batteries and clearly demonstrate that even partially lithiated graphite experiences considerable crystallographic strain

DataSheet1_Synthesis of perovskite-type high-entropy oxides as potential candidates for oxygen evolution.docx

High-entropy materials offer a wide range of possibilities for synthesizing new functional ceramics for different applications. Many synthesis methods have been explored to achieve a single-phase structure incorporating several different elements, yet a comparison between the synthesis methods is crucial to identify the new dimension such complex ceramics bring to material properties. As known for ceramic materials, the synthesis procedure usually has a significant influence on powder morphology, elemental distribution, particle size and powder processability. Properties that need to be tailored according to specific applications. Therefore, in this study perovskite-type high-entropy materials (Gd0.2La0.2–xSrxNd0.2Sm0.2Y0.2) (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 (x = 0 and x = 0.2) are synthesized for the first time using mechanochemical synthesis and a modified Pechini method. The comparison of different syntheses allows, not only tailoring of the constituent elements of high-entropy materials, but also to optimize the synthesis method as needed to overcome limitations of conventional ceramics. To exploit the novel materials for a variety of energy applications, their catalytic activity for oxygen evolution reaction was characterized. This paves the way for their integration into, e.g., regenerative fuel cells and metal air batteries.</p