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Abstract The development of alternative energy sources is crucial for reducing reliance on fossil fuels, particularly for mobile applications such as personal electronics and transportation. This necessitates the advancement of battery materials based on abundant and inexpensive constituent elements. To achieve this requires investigating materials in a broader compositional and structural design space. Early transition metal oxides, including the intercalation electrode $\alpha -$V₂O₅, however, the performance of V₂O₅is hindered by phase transformations during battery cycling that lead to capacity fade and short device lifetimes. This study investigates the modification of V₂O₅through Mo substitution in a series of the form V ${}_{2-x}$Mo_xO₅forx= 0.05, 0.1, 0.2, 0.4, 0.6, and 0.8. X-ray diffraction data reveal progressive structural changes with increasing Mo content, which in turn change the progression of phase transformations during the first discharge. The different product also results in different cycling profile shapes that indicate differences in the charge storage mechanism as a function of Mo content. As a result, samples with higher Mo-substitution, especially V_1.2Mo_0.8O₅, have narrower hysteresis, higher capacity, and improved capacity retention. While there is a limited solubility of Mo in the V₂O₅structure, with secondary phases and defects at many compositions, we show that Mo substitution alters the cycling behavior of V₂O₅to deep discharge, which can inform the design of intercalation materials for energy storage applications. 

Abstract Understanding surface stability becomes critical as 2D materials like SnSe are developed for piezoelectric and optical applications. SnSe thin films deposited by molecular beam epitaxy showed no structural changes after a two-year exposure to atmosphere, as confirmed by X-ray diffraction and Raman spectroscopy. X-ray photoelectron spectroscopy and reflectivity show a stable 3.5 nm surface oxide layer, indicating a self-arresting oxidative process. Resistivity measurements show an electrical response dominated by SnSe post-exposure. This work shows that SnSe films can be used in ambient conditions with minimal risk of long-term degradation, which is critical for the development of piezoelectric or photovoltaic devices. Graphical Abstract