Search

All-solid-state lithium-ion batteries raise the issue of high resistance at the interface between solid electrolyte and electrode materials that needs to be addressed. The article investigates the effect of a low-melting Li3BO3 additive introduced into LiCoO2- and Li4Ti5O12-based composite electrodes on the interface resistance with a Li7La3Zr2O12 solid electrolyte. According to DSC analysis, interaction in the studied mixtures with Li3BO3 begins at 768 and 725 °C for LiCoO2 and Li4Ti5O12, respectively. The resistance of half-cells with different contents of Li3BO3 additive after heating at 700 and 720 °C was studied by impedance spectroscopy in the temperature range of 25–340 °C. It was established that the introduction of 5 wt% Li3BO3 into LiCoO2 and heat treatment at 720 °C led to the greatest decrease in the interface resistance from 260 to 40 Ω cm2 at 300 °C in comparison with pure LiCoO2. An SEM study demonstrated that the addition of the low-melting component to electrode mass gave better contact with ceramics. It was shown that an increase in the annealing temperature of unmodified cells with Li4Ti5O12 led to a decrease in the interface resistance. It was found that the interface resistance between composite anodes and solid electrolyte had lower values compared to Li4Ti5O12|Li7La3Zr2O12 half-cells. It was established that the resistance of cells with the Li4Ti5O12/Li3BO3 composite anode annealed at 720 °C decreased from 97.2 (x = 0) to 7.0 kΩ cm2 (x = 5 wt% Li3BO3) at 150 °C.

Cu/Mg-composites, the copper matrix of which contains 1, 7 and 2730 magnesium filaments, were obtained by hyrdoextrusion at room temperature. The structure, mechanical and electrical properties of the deformed composite rods and thin wires were investigated. The yield strength and electrical resistivity were theoretically calculated and these estimations were compared with the experimental results. The XRD-method allowed discovering a change of the lattice constant of the Cu-matrix under deformation of the composites. It has been concluded that, under severe plastic deformation, a supersaturated Cu-based solid solution forms on the Cu/Mg-interface. As a result, the strength of the deformed Cu/Mg-composite with minimal volume fraction but maximal surface area of magnesium is abnormally high. A thick Cu-sleeve provides low electrical resistivity of this Cu/Mg-composite. The obtained results can be used for the development of high-strength Cu-based conductors. © 2019 The Authors Ural Branch, Russian Academy of Sciences, UB RAS The work was carried out in the framework of a state task according to the theme ?Pressure? No. AAAA-A18-118020190104-3. The studies of structure and mechanical properties of the samples were carried out at the Electron Microscopy Department and Mechanical Test Department of the Collective-Use Center of the Institute of Metal Physics (Ural Branch, Russian Academy of Sciences). The X-ray diffraction studies were carried out in the ?Composition of Compounds? Center of Collaborative Access, Institute of High-Temperature Electrochemistry, Ural Branch, Russian Academy of Sciences.

Solid electrolytes are widely used in electrochemical devices. Among these materials, electrolytes with the lithium-ion conductivity can be used in high-energy lithium and lithium-ion power sources. The perspective Li6.75La3Zr1.75Nb0.25O12 solid electrolyte was synthesized by modified sol-gel synthesis method using the sparingly soluble Nb2O5 as one of the initial compounds. The influence of pressure and final sintering temperature on phase composition, density and lithium-ion conductivity was studied. Solid electrolyte obtained at 1150°C was single phase and had a cubic structure with the space group Ia-3d. Thus in the presented work, the cubic modification of Li6.75La3Zr1.75Nb0.25O12 was obtained by thermal treatment for 1 h at 1150°C (versus 36 h at 1200°C in the literature). Moreover at this temperature the samples had the highest density and total lithium-ion conductivity (3.9•10-5 Scm-1 at 25°C). According to the SEM study ceramic samples have a dense structure with a particle size ∼1-3 μm. Solid electrolyte was also obtained by isostatic pressing at a pressure of 500 MPa but the values of density and total lithium-ion conductivity were comparable with that of the samples compressed statically. © Published under licence by IOP Publishing Ltd. Council on grants of the President of the Russian Federation: MK-1382.2019.3 The reported study was funded by the grant of the President of the Russian Federation according to the research project No MK-1382.2019.3. The research has been carried out with the equipment of the Shared Access Center “Composition of Compounds” of the Institute of High-Temperature Electrochemistry of Ural Branch of RAS, Ekaterinburg, Russian Federation.