Although the thermal conductivity of molten salt mixtures is of interest for many potential technological applications, precise values are often hard to obtain. In this study, the thermal diffusivity of FliNaK was studied in a molten state using the laser flash method and found to be very slightly dependent on temperature. The heat capacity of FliNaK was measured using the DSC method. There was a minor difference between our results and data from the literature. From calculations based on thermal diffusivity, density and heat capacity values, thermal conductivity was shown to decrease with temperature.

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.