Supercritical carbon dioxide (scCO2) is a non-toxic, inert, and widely used solvent in green chemistry, offering tunable properties such as density, diffusivity, viscosity, and polarity, adjustable through temperature, pressure, or co-solvent addition. This study employs the Design of Experiment (DoE) methodology to optimize scCO2-assisted synthesis of Li-S battery cathodes, presenting the first systematic investigation of how scCO2 conditions affect the structural and surface properties of reduced graphene oxide (rGO) during sulfur decoration. Results show that temperature and pressure significantly influence sulfur integration and cathode performance. By combining DoE with detailed electrochemical impedance analysis using complex nonlinear least squares fitting, the study provides deeper insight into composite electrochemical behavior under varying conditions. An optimal rGO structure with low charge transfer resistance, enabling efficient ion and electron transport, was obtained at 150 bar and 60 °C, balancing sulfur loading and pore accessibility. Conversely, harsher conditions (180 bar, 80 °C) caused sulfur agglomeration and higher resistance, reducing performance. These findings highlight the necessity of precisely controlling scCO2 synthesis parameters to enhance cathode structure and improve electrochemical performance and long-term stability of Li-S batteries.

After being an indispensable intermediate in the oxidative exfoliation route towards graphene, graphene oxide has gained its deserved value in materials science for numerous applications, from catalysis, through energy storage and conversion, to sensor use. In this work, three graphene oxides of tuned morphology and chemistry are used as a simplified model for porous carbon materials in hydrogen storage and as a Li-ion battery anode. The BET surface areas were, respectively, 9, 13, and 535 m²/g, while the corresponding O/C values from the X-ray photoelectron spectroscopy were 0.51, 0.17, and 0.12. Additionally, the samples were thoroughly characterized using scanning and transmission electron imaging, powder X-ray diffraction, thermal stability, and Raman and Fourier transform infrared spectroscopic methods. Hydrogen adsorption isotherms (−196 °C) and their comparison with nitrogen uptake revealed that pore accessibility, porous confinement, and surface chemistry, i.e., both morphology and surface chemistry, contribute to efficient adsorption. In the anode application, by contrast, surface chemistry was the single most defining factor for performance.

In this study, the mechanical response of MoO3 thin-film cathodes deposited on aluminum substrates was systematically investigated using nanoindentation techniques under an inert atmosphere. Both amorphous and crystalline phases were examined across non-, partially, and fully lithiated states to elucidate the influence of lithium intercalation on elastic and plastic behavior. A range of indenter geometries, including spherical and Berkovich tips, were employed to extract plastic, elastic, and interfacial properties. The elasticity increased with lithium content, with partially lithiated systems exhibiting the highest values. Residual indentation depths were lowest for partially lithiated samples, indicating a distinct mechanical regime compared to both non- and fully lithiated states. The amorphous phase demonstrated higher stiffness, with deformation-induced cracks confined within the layer, while the crystalline phase accommodated deformation more uniformly via grain boundary sliding. The mechanical response in the crystalline phase suggests a significant role of grain-boundary-mediated deformation mechanisms. Furthermore, no degradation in layer adhesion was observed with increasing lithium content, indicating a mechanically stable interface across all lithiation states. These findings provide new insights into the mechanical integrity of cathode–current collector systems in solid-state lithium-ion batteries and underscore the critical role of intercalation state, structural phase, and microstructural pathways in determining mechanical performance.