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High-entropy alloys have made significant progress in high mechanical properties, wear resistance, and corrosion resistance properties. Excellent tribological properties, especially high-temperature lubrication, have become another sought performance. In this work, VAlTiCrW high-entropy alloy film with body-centered cubic (BCC) structure was prepared on superalloy substrate by magnetron sputtering. It is found that the VAlTiCrW film shows very low friction coefficient of 0.15 and a low wear rate of 10−5 orders of magnitude at 800 °C. After 800 °C oxidation, the film can still obtain a friction coefficient of no more than 0.2 at 700 °C. XRD and TEM revealed the formation of ternary oxide AlV3O9 with preferred orientation of (002) crystal plane with large spacing of 0.71 nm on the wear surface of the film, a high-temperature lubricating phase that has not been reported, realizes the low friction coefficient. This AlV3O9 can be formed by tribochemical reaction under the thermal-mechanical action at 700 °C, but pre-oxidation at 800 °C is the prerequisite in order to form the precursors of V-rich and Al-rich oxide layer. [ABSTRACT FROM AUTHOR]

Elevating the charge voltage of LiCoO2 increases the energy density of batteries, which is highly enticing in energy storage implementation ranging from portable electronics to e‐vehicles. However, hybrid redox reactions at high voltages facilitate oxygen evolution, electrolyte decomposition and irreversible phase change, and accordingly lead to rapid battery capacity decay. Here significantly improved high‐voltage cycling stability of Mg‐Al‐Eu co‐doped LiCoO2 is demonstrated. It is found that element co‐doping induces a near‐surface high‐entropy zone, including an innately thin disordered rock‐salt shell and a dopant segregation surface. The high‐entropy complex can effectively suppress oxygen evolution and near‐surface structure deconstruction. The phase change reversibility between O3 and H1‐3 and thermal stability of the cathode are greatly enhanced as well. As a result, the co‐doped LiCoO2 exhibits a remarkable cycling performance, retaining 86.3% and 72.0% of initial capacity over 800 and 2000 cycles, respectively, with a high cut‐off voltage of 4.6 V. The feasible co‐doping approach broadens the perspective for the development of stable lithium‐ion batteries with high operating voltages. [ABSTRACT FROM AUTHOR]

Oxygen-carbon-contained CrMnFeCoNi coatings were electrodeposited in an organic solvent of DMF-CH3CN (N,N-dimethylformamide-acetonitrile) containing chlorides of chromium, manganese, iron, cobalt, and nickel, with or without supporting electrolyte lithium perchlorate (LiClO4). The coatings' composition, structure, hardness, and electrocatalytic properties were examined. The presence of lithium in coatings obtained with LiClO4 showed it unsuitable as a supporting electrolyte in this fabrication process. Without LiClO4, oxygen-carbon-contained CrMnFeCoNi coatings were obtained at constant potentials at −2.0, −2.5, and −3.0 V (vs. SSE) by enhancing the concentrations of the target metal ions in the solution. These coatings were mainly amorphous with nanocrystals, which were comprised of >50 atom% oxygen atoms, >7 atom% carbon atoms, and near equiatomic Cr, Mn, Fe, Co, and Ni, showing a high level of hardness and advanced electrocatalytic activity in the oxygen evolution reaction. [ABSTRACT FROM AUTHOR]