The need for high power density cathodes for Li-ion batteries can be fulfilled by application of a high charging voltage above 4.5 V. As lithium cobalt oxide (LCO) remains a dominant commercial cathode material, tremendous efforts are invested to increase its charging potential toward 4.6 V. Yet, the longterm performance of high voltage LCO cathodes still remains poor. Here, an integrated approach combining the application of an aluminum fluoride coating and the use of electrolyte solutions comprising 1:1:8 mixtures of difluoroethylene:fluoroethylene carbonate:dimethyl carbonate and 1 m LiPF 6 is reported. This results in superior behavior of LCO cathodes charged at 4.6 V with high initial capacity of 223 mAh g −1 , excellent long-term performance, and 78% capacity retention after 500 cycles. Impressive stability is also found at 450 °C with an initial capacity of 220 mAh g −1 and around 84% capacity retention after 100 cycles. Systematic post-mortem analysis of LCO cathodes and Li anodes after prolonged cycling reveals two main degradation routes related to changes at the surface of the cathodes and formation of passivation layers on the anodes. This study demonstrates the importance of appropriate selection of electrolyte solutions and development of effective coatings for improved performance of high voltage LCO-based Li batteries.

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Metallic mercury has always attracted much attention in various fields because of its unique characteristic of forming amalgams. Here, different phases of pure crystalline Hg-Ag amalgam microspheres are synthesized by ultrasonically reacting liquid mercury with an aqueous solution of silver nitrate. Sonicating different molar ratios of liquid metallic Hg with AgNO results in the formation of pure crystalline phases of solid silver amalgams with uniform morphology. The resulting Hg-Ag amalgams from various compositions after sonication are physically characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Differential Scanning Calorimetry (DSC). The XRD of the amalgams obtained from the molar ratios of Hg:Ag (1:1.5) and Hg:Ag (1.5:1 and 2:1) match the Schachnerite and Moschellandbergite phases, respectively, whereas the Hg-Ag amalgam prepared from a 1:1Hg:Ag molar ratio results in a mixture of the Schachnerite and Moschellandbergite phases. The obtained amalgam microspheres are between 6 and 10µm in size. The detailed thermal and chemical behaviour of the Ag-Hg systems is also investigated.

Engineering of efficient, robust and inexpensive Pt-free catalysts for the hydrogen evolution reaction has drawn great attention, and there is a rapidly growing demand for electrochemical water-splitting reactions. Here, we report, for the first time, synthesis of ruthenium oxide nanoparticles supported on molybdenum oxide nanosheets (MoO 3 @RuO 2 ). This composite catalyst was prepared sonochemically, followed by calcination of the product in air at 400°C for one hour. The as-synthesized MoO 3 @RuO 2 composite catalyst was used to explore the electro-catalytic hydrogen evolution reaction in acidic medium.Notably, compared to MoO 3 or RuO 2 , the composite exhibited high exchange current density of 0.57 mA cm À 2 , and a current density of 10 mA cm À 2 was achieved at low overpotential of 110 mV in 0.5 M H 2 SO 4 . The Tafel slope of the MoO 3 @RuO 2 catalyst was 62 mV dec À 1 and it showed excellent stability. This remarkable performance can be attributed to the synergetic effect generated by the strong interaction between MoO 3 nanosheets and RuO 2 nanoparticles, which resulted in enhanced long-term stability as well.be a potential alternative in various energy conversion applications to the benchmark Pt catalyst, which is significantly more expensive than ruthenium metal.

Among extensively studied Li‐ion cathode materials, LiCoO2 (LCO) remains dominant for portable electronic applications. Although its theoretical capacity (274 mAh g−1) cannot be achieved in Li cells, high capacity (≤240 mAh g−1) can be obtained by raising the charging voltage up to 4.6 V. Unfortunately, charging Li‐LCO cells to high potentials induces surface and structural instabilities that result in rapid degradation of cells containing LCO cathodes. Yet, significant stabilization is achieved by surface coatings that promote formation of robust passivation films and prevent parasitic interactions between the electrolyte solutions and the cathodes particles. In the search for effective coatings, the authors propose RbAlF4 modified LCO particles. The coated LCO cathodes demonstrate enhanced capacity (>220 mAh g−1) and impressive retention of >80/77% after 500/300 cycles at 30/45 °C. A plausible mechanism that leads to the superior stability is proposed. Finally the authors demonstrate that the main reason for the degradation of 4.6 V cells is the instability of the anode side rather than the failure of the coated cathodes.