In the realm of advanced anode materials for lithium-ion batteries, this study explores the electrochemical performance of a high-entropy oxide (HEO) with a unique spinel structure. The equiatomic composition of CrMnFeCoCu was synthesized and subjected to a comprehensive materials characterization process, including X-ray diffraction and microscopy techniques. The multicomponent alloy exhibited a multiphase structure, comprising two face-centered cubic (FCC) phases and an oxide phase. Upon oxidation, the material transformed into a spinel oxide with a minor presence of CuO. The resulting high-entropy oxide demonstrated excellent electrochemical behavior when utilized as an anode material. Cyclic voltammetry revealed distinctive reduction peaks attributed to cation reduction and solid electrolyte interphase (SEI) layer formation, while subsequent cycles showcased high reversibility. Electrochemical impedance spectroscopy indicated a decrease in charge transfer resistance during cycling, emphasizing the remarkable electrochemical performance. Galvanostatic charge/discharge tests displayed characteristic voltage profiles, with an initial irreversible capacity attributed to SEI layer formation. The HEO exhibited promising rate capability, surpassing commercial graphite at higher current densities. The battery achieved 80% (275 mAh g⁻¹) of its initial stable capacity at a current density of 500 mA g⁻¹ by the 312th cycle. Post-mortem analysis revealed structural amorphization during cycling, contributing to the observed electrochemical behavior. This research highlights the potential of HEOs as advanced anode materials for lithium-ion batteries, combining unique structural features with favorable electrochemical properties.

This study presents the design, preparation, and characterization of thirty new medium-entropy alloys (MEAs) in three systems: Al-Ti-Nb-Zr, Al-Ti-Nb-V, and Al-Ti-Nb-Hf. The hardness of the alloys ranged from 320 to 800 HV_0.3. Among the alloys studied, Al₁₅Ti₄₀Nb₃₀Zr₁₅ exhibited the highest-reversible hydrogen storage capacity (1.03 wt.%), with an H/M value of 0.68, comparable to LaNi₅, but with a reduced density (5.11 g·cm⁻³) and without rare earth elements. This study further reveals a strong correlation between hardness and hydrogen absorption/desorption; higher hardness is responsible for reduced hydrogen uptake. This finding highlights the interplay between a material’s properties and hydrogen storage behavior in MEAs, and has implications for the development of efficient hydrogen storage materials.

This study introduces an innovative approach to alloy design by experimentally validating the semi-empirical concept of Griessen and Driessen, which predicts the hydrogen affinity of solid solutions. The work focuses on designing and synthesizing four equiatomic high-entropy alloys (HEAs) with compositions tailored to exhibit highly endothermic enthalpies of solution and formation, resulting in resistance to hydrogen absorption. Unlike conventional studies that prioritize hydrogen storage capacity, this research uniquely targets alloys optimized for minimal hydrogen interaction, addressing critical needs in hydrogen storage and transportation technologies prone to hydrogen embrittlement. Experimental results confirm the negligible hydrogen absorption of these alloys, with a maximum of 0.23 wt.% (H/M = 0.13) at 2 MPa and 175 °C. This study not only demonstrates the applicability of a theoretical model to guide alloy design but also highlights the potential of these materials for low-pressure hydrogen storage systems, where mechanical integrity and resistance to hydrogen degradation are paramount. The findings bridge the gap between theoretical predictions and practical applications, offering a novel perspective on alloy development for hydrogen-related technologies.

X-ray Absorption Fine Structure Spectroscopy (XAFS) has proven instrumental for the study of atomic-scale structures across diverse materials. This study conducts a meticulous comparative analysis between total electron yield (TEY) and absorption coefficients at the K absorption edge of polycrystalline Fe and Zr₆₀Cu₂₀Fe₂₀ alloy. Our findings not only highlight differences between TEY and transmission XAFS measurements but also demonstrate the capabilities and limitations inherent in these measurement modes within the context of XAFS. This article provides an experimental exploration of widely used X-ray absorption spectroscopy methods, shedding light on the nuances of TEY and transmission XAFS. Through presenting experimental results, we aim to offer insights crucial to the material science community, guiding experimentalists in optimizing measurements while raising awareness about potential misinterpretations.

Medium-entropy alloys (MEAs) represent a promising class of materials for solid-state hydrogen storage due to their high hydrogen affinity, structural stability, and tunable properties. In this work, a compositional series of (TiZrNbTa)_{100−x}Al_x (x = 0–10 at. %) MEAs were prepared and systematically investigated to clarify the influence of aluminum addition on microstructure, mechanical response, and hydrogen sorption behavior. The alloys were synthesized by arc melting, homogenized by annealing, and characterized using microscopy, X-ray diffraction, density measurements, microhardness testing, nanoindentation, and hydrogen absorption/desorption experiments. Hydrogen sorption was evaluated by isobaric absorption measurements at 2 MPa H₂ over two consecutive cycles, complemented by thermogravimetric desorption analysis of hydrogenated samples. The results show that aluminum addition significantly affects activation behavior, hydrogen uptake, and residual hydrogen retention, while simultaneously increasing hardness and elastic modulus in a non-linear manner. The alloy containing 5 at. % Al exhibits the most balanced performance, combining reduced activation temperature in the second absorption cycle, relatively high hydrogen capacity, and moderate mechanical stiffness. These findings demonstrate that controlled aluminum alloying is an effective strategy for tailoring hydrogen–metal interactions and optimizing the performance of TiZrNbTa-based MEAs for solid-state hydrogen storage applications.

Hydrogen is a key element in the changing energy sector and presents an accessible alternative to conventional fossil fuel sources. In this work, a system of ten high-entropy alloys was prepared based on the Hume-Rothery rules. One of the biggest advantages of these alloys is their storage capacity, which reaches the highest value among all known alloys intended for hydrogen storage. Alloys based on Al-Ti-Nb-Zr elements with different atomic fractions show interesting accumulation capabilities with fast absorption kinetics and low specific gravity. Each alloy in this study underwent high-pressure gravimetric absorption and desorption tests. The main goals of this work were to prepare alloys with the lowest-possible specific gravity and the highest-possible storage capacity. One alloy from our system shows storage capacity values similar to commercial alloys, without any rare-earth elements.