Thin-film solid electrolytes are crucial for safe high-energy all-solid-state power sources. The paper focuses on the issue of maintaining low porosity and high strength of solid electrolyte films obtained by tape casing. Ion-conducting glass is capable of filling the voids induced by heat treatment, creating a composite characterized by high ionic conductivity and enhanced mechanical strength. The effect of lithium borosilicate glass addition on the structure formation, morphology, and lithium-ion conductivity of Li6.6Al0.05La3Zr1.75Nb0.25O12 films is studied. The films based on the solid electrolyte were produced by tape casting on a Mylar substrate and then laminated together and pressed at room temperature to enhance their mechanical strength. The effect of the final sintering temperature on the electrical and physical characteristics of 65Li2O–27B2O3–8SiO2-free solid electrolyte films was studied. An increase of the sintering temperature from 900 to 1150 ℃ is accompanied by an expected increase in the ionic conductivity of the material from 2.1·10–10 to 1.5·10–7 S·cm−1 at 25 ℃. An introduction of 3-wt.

The thermal diffusivity of LiF-NaF-KF (FLiNaK), NaF-KF and FliNaK-NdF3 mixtures was studied by laser flash method near the melting point. The obtained results demonstrate that the thermal diffusivity of the melts slowly decreases within a certain temperature range. Thermal diffusivity of eutectic FLiNaK and NaF-KF mixtures was found to drop sharply at the temperatures of 30–50 ° below the melting point. These values correspond to the overcooling interval. Thermal conductivity was calculated using the thermal diffusivity heat capacity and density data. Thermal diffusivity of the FliNaK-NdF3 mixture decreases slowly in the phase transition temperature range.

The development of solid-state lithium-ion power sources is currently hindered by technological barriers including high resistance at the interface between the solid electrolyte and electrodes and complex manufacturing process. Thin films of solid electrolyte reduce ionic resistance by minimizing structural defects and increasing the contact area between the electrodes and the electrolyte. The present work investigates the structure, morphology and lithium-ion conductivity of Li6.6Al0.05La3Zr1.75Nb0.25O12 films synthesized on a Ti substrate by electrophoretic deposition. The effect of the pre-synthesis processing of the solid electrolyte powder on the final film properties is studied by comparing initial powders of Li6.6Al0.05La3Zr1.75Nb0.25O12 solid electrolyte annealed at a final temperature of 900 °C and 1150 °C. It is shown that milling the initial solid electrolyte powder improves the structure of the final film. The films had a homogenous structure with a thickness of 40–60 μm. The film produced from the powder with the final annealing temperature of 1150 °C and annealed at 300 °C delivered the highest conductivity among the samples investigated (3.4·10–6 S·cm–1 and 4.5·10–5 S·cm–1 for through- and in-plane conductivity, respectively, at 300 °C).

The development of solid-state lithium-ion power sources is currently hindered by technological barriers including high resistance at the interface between the solid electrolyte and electrodes and complex manufacturing process. Thin films of solid electrolyte reduce ionic resistance by minimizing structural defects and increasing the contact area between the electrodes and the electrolyte. The present work investigates the structure, morphology and lithium-ion conductivity of Li6.6Al0.05La3Zr1.75Nb0.25O12 films synthesized on a Ti substrate by electrophoretic deposition. The effect of the pre-synthesis processing of the solid electrolyte powder on the final film properties is studied by comparing initial powders of Li6.6Al0.05La3Zr1.75Nb0.25O12 solid electrolyte annealed at a final temperature of 900 °C and 1150 °C. It is shown that milling the initial solid electrolyte powder improves the structure of the final film. The films had a homogenous structure with a thickness of 40–60 μm. The film produced from the powder with the final annealing temperature of 1150 °C and annealed at 300 °C delivered the highest conductivity among the samples investigated (3.4·10–6 S·cm–1 and 4.5·10–5 S·cm–1 for through- and in-plane conductivity, respectively, at 300 °C).

Abstract—The discharge characteristics of heat activated batteries (HABs) containing NiCl2–NiF2 mixtures as a positive electrode are studied. For the current density range from 0.25 to 1.5 A cm–2, this cathodic material is characterized by stable electrical characteristics in a temperature range of 480–600°C. The optimum composition of the cathodic mixture for the discharge conditions of HAB cells under study is determined. The reduction products of the NiCl2–NiF2 cathodic mixtures are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and simultaneous thermal analysis (STA). The components of the cathodic mixture are reduced via the two-electron electrochemical reaction. The reduction products are metallic nickel and lithium halides. Lithium salts form solid solutions based on lithium chloride. Nickel forms the dendrite sponge that grows during HAB cell discharge and shifts deep inside the positive electrode. Pores of the dendrite sponge are filled with the salt fraction with a melting point of 470–490°C. The melting point of the salt fraction predetermines the lower boundary of the working temperature range of the HAB cell under study.

All-solid-state lithium batteries are in great demand, but the problem of high interfacial resistance between the cathode and solid electrolyte needs to be addressed. The effect of heat treatment of the cathode half-cells on the LiFePO 4 | Li 7 La 3 Zr 2 O 12 interfacial resistance was studied. According to differential scanning calorimetry, the interaction between the cathode material and Li 7 La 3 Zr 2 O 12 begins at 699 degrees C. It was also shown via X-ray diffraction data that increasing the annealing temperature from 600 to 700 degrees C leads to the appearance of impurities related to the interaction of the solid electrolyte with LiFePO 4 (La 2 Zr 2 O 7 and LaFeO 3 ). A scanning electron microscopy study demonstrated that LiFePO 4 has good contact with ceramic electrolyte without and after heat treatment. The lowest resistance at the LiFePO 4 | Li 7 La 3 Zr 2 O 12 interface (-2000 and 30 Ohm cm 2 at 100 and 300 degrees C, respectively) was obtained for half-cells without heat treatment. Thus, heat treatment leads to an increase in the interfacial resistance caused by the interaction of LiFePO 4 with Li 7 La 3 Zr 2 O 12

All-solid-state lithium batteries are in great demand, but the problem of high interfacial resistance between the cathode and solid electrolyte needs to be addressed. The effect of heat treatment of the cathode half-cells on the LiFePO4 | Li7La3Zr2O12 interfacial resistance was studied. According to differential scanning calorimetry, the interaction between the cathode material and Li7La3Zr2O12 begins at 699 °C. It was also shown via X-ray diffraction data that increasing the annealing temperature from 600 to 700 °C leads to the appearance of impurities related to the interaction of the solid electrolyte with LiFePO4 (La2Zr2O7 and LaFeO3). A scanning electron microscopy study demonstrated that LiFePO4 has good contact with ceramic electrolyte without and after heat treatment. The lowest resistance at the LiFePO4 | Li7La3Zr2O12 interface (∼2000 and 30 Ohm cm2 at 100 and 300 °C, respectively) was obtained for half-cells without heat treatment. Thus, heat treatment leads to an increase in the interfacial resistance caused by the interaction of LiFePO4 with Li7La3Zr2O12

Molten fluoride salts are under development for use as fuel coolant and thermal storage in industrial nuclear energy production. This study focuses on the experimental and molecular dynamic investigation of thermal conductivity and ion diffusion in the eutectic molten salts of NaF–KF and NaF–KF–MgF 2 . Experimental and calculated data demonstrate that the temperature-dependent thermal conductivity can be accurately represented as a decaying linear function for both melts. The significant diffusion coefficient of fluorine ions in the NaF–KF molten system can be attributed to the considerable number of Coulomb repulsions among the abundant negative ions in the irregular system. The findings of this study provide insights into the behavior of NaF–KF and NaF–KF–MgF 2 molten salt mixtures under operating conditions in high-temperature power plants.

The thermophysical properties of molten salts promising for the nuclear industry are crucial, but the available data are limited and contradictory. The thermal diffusivity of the molten mixtures (NaF-KF)eut–UF4 containing 30, 40, and 50 mol

Currently, the properties of molten lithium, sodium and potassium fluoride eutectic mixtures with different additions are immensely important for the development of molten salt nuclear reactors. In the present work, the density of molten FLiNaK mixtures with additions of neodymium fluoride was studied by the Archimedean method. The neodymium fluoride addition increased the density of the 46.5 mol

The paper discusses the feasibility of 1-ethyl-3-methylimidazolium ([EMIm]Cl) and 1-butyl-3-methylimidazolium ([BMIm]Cl) chloroaluminate ionic liquids (ILs) as electrolytes for aluminum-ion batteries capable of delivering high performance at subzero temperatures. The melting temperatures of AlCl3-[EMIm]Cl and AlCl3-[BMIm]Cl ILs with the molar ratio of aluminum chloride to the chloride of imidazolium salt (N) equal to 1.3 and 1.5 were determined using DSC. The melting temperature of AlCl3-[EMIm]Cl is -21 and -32 degrees C at N = 1.3 and N = 1.5, respectively. The conductivity of AlCl3-[EMIm]Cl IL increases sharply at heating and decreases sharply near its melting temperature at cooling. The DSC curves for [BMIm]Cl-based ILs do not contain any peaks related to the melting or crystallization of the IL, and temperature dependences of conductivity contain no inflection points. Galvanostatic cycling and cyclic voltammetry demonstrated efficient performance of the aluminum-ion battery with an aluminum anode, graphene cathode and AlCl3-[BMIm]Cl IL, which delivered coulombic efficiency approaching 100 % at temperatures as low as -30 degrees C. The capacity of the graphene cathode was found to be 82.4, 63.0 and 48.5 mA center dot h center dot g- 1 at 0, -20 and -30 degrees C, respectively.

Li7La3Zr2O12 is one the most promising materials for Li-conducting solid electrolytes. The incorporation of Ta5+ and Nb5+ into the Zr4+ sites stabilizes its cubic structure and significantly enhances Li-conductivity, due to the formation of Li vacancies. In this research, we have studied the band gap features of Ta and Nd-doped Li7La3Zr2O12. Our findings indicate that Nb ions are present not only in the +5 valence state, but also in the +4 state, leading to the formation of oxygen vacancies. In the case of the Ta-doping, such an effect was not observed. This could be the reason for the approximately one order of magnitude higher lithium conductivity observed in the case of the Ta doping, in comparison to the Nb doping.

The development of solid electrolytes with high conductivity is one of the key factors in the creation of new power-generation sources. Lithium-ion solid electrolytes based on Li7La3Zr2O12 (LLZ) with a garnet structure are in great demand for all-solid-state battery production. Li7La3Zr2O12 has two structural modifications: tetragonal (I41/acd) and cubic (Ia3d). A doping strategy is proposed for the stabilization of highly conductive cubic Li7La3Zr2O12. The structure features, density, and microstructure of the ceramic membrane are caused by the doping strategy and synthesis method of the solid electrolyte. The influence of different dopants on the stabilization of the cubic phase and conductivity improvement of solid electrolytes based on Li7La3Zr2O12 is discussed in the presented review. For mono-doping, the highest values of lithium-ion conductivity (~10−3 S/cm at room temperature) are achieved for solid electrolytes with the partial substitution of Li+ by Ga3+, and Zr4+ by Te6+. Moreover, the positive effect of double elements doping on the Zr site in Li7La3Zr2O12 is established. There is an increase in the popularity of dual- and multi-doping on several Li7La3Zr2O12 sublattices. Such a strategy leads not only to lithium-ion conductivity improvement but also to the reduction of annealing temperature and the amount of some high-cost dopant. Al and Ga proved to be effective co-doping elements for the simultaneous substitution in Li/Zr and Li/La sublattices of Li7La3Zr2O12 for improving the lithium-ion conductivity of solid electrolytes.

The critical issue of high resistance at the interface between cathode and solid electrolyte for creating all-solid-state power sources can be addressed by introducing a low-melting additive (Li3BO3) and lithium-conducting solid electrolyte (Li7La3Zr2O12) in the LiNi1/3Co1/3Mn1/3O2 cathode mass. The chemical and thermal stability of the solid electrolyte in contact with LiNi1/3Co1/3Mn1/3O2 and Li3BO3 was studied using XRD and DSC analysis. It was found that the introduction of 5 wt% Li3BO3 in LiNi1/3Co1/3Mn1/3O2 leads to a close contact between the solid electrolyte and cathode and a decrease in the interfacial resistance from 45000 to 85 Ω cm2 at 300 °C compared to pure LiNi1/3Co1/3Mn1/3O2. The addition of 5 wt% lithium-conductive electrolyte to the cathode mass does not lead to significant changes in interface resistance. No degradation processes in the components of the experimental cell with composite cathode and Li anode were found during electrochemical experiments.

Thin film technology of lithium-ion solid electrolytes should be developed for the creation of all-solid-state power sources. Solid electrolytes of the Li7La3Zr2O12 (LLZ) family are one of the promising membranes for all-solid-state batteries. LLZ films were obtained by electrophoretic deposition on Ti, Ni and steel substrates. The influence of different metal substrates on microstructure, phase composition and conductivity of the LLZ films after their heat treatment was studied. It was shown that the annealing of dried LLZ films in an Ar atmosphere leads to the transition from tetragonal modification to a low-temperature cubic structure. It was established that an impurity phase (Li2CO3) was not observed for LLZ films deposited on Ti foil after heat treatment, in contrast to films deposited on Ni and steel substrates. The highest lithium-ion conductivity values were achieved for the LLZ films annealed at 300 °C, 1.1 × 10−8 S cm−1 (at 100 °C) and 1.0 × 10−6 S cm−1 (at 200 °C).

Solid electrolytes based on Li7La3Zr2O12 are promising membranes for all–solid–state batteries. However, the main parameters of all transport stages in composite and doped Li7La3Zr2O12 could not be determined by conventional impedance fitting. A tremendous assistance in the analysis of impedance spectra over the past few years has become the method of distribution of relaxation times (DRT). In the present study, a composite electrolyte Li7La3Zr2O12 – Li2O–B2O3–SiO2 was investigated by impedance spectroscopy. A detailed analysis of the impedance spectra by DRT showed that the additional peak appears on the DRT function with the introduction of glass; this interfacial resistance is responsible for the transfer of lithium ions across the Li7La3Zr2O12/glass interface. The resistance, capacitance and relaxation frequency of all the transport stages in the composite electrolytes were determined based on the analysis of the DRT functions. It was found that the Li7La3Zr2O12/glass resistance decreases with increasing fraction of glassy additive. It was established that the DRT technique can be successfully used to deeper understanding of the transport stages of lithium ions in composite and doped solid electrolytes for all–solid–state batteries.

Currently, interest to lithium and lithium-ion all-solid-state power sources is rapidly growing all over the world. However, several issues should be addressed before all-solid-state batteries production: high resistance values of the solid electrolyte membrane and poor contact between electrolyte and electrode materials. The transition to thin-film technologies is one of the promising ways to solve these problems. Tape casting can be proposed to obtain thin-film solid electrolytes. In this research, the features of the structure formation, morphology and lithium-ion conductivity of Li7La3Zr2O12 films were investigated. Li7La3Zr2O12 films with the thickness of 35 µm were obtained by tape casting on Ni substrate. The influence of organic components’ content on homogeneous coatings formation was established. Heat treatment conditions for dried films were chosen based on differential scanning calorimetry and optical dilatometry. Phase change from tetragonal to low-temperature cubic modification occurs after annealing the Li7La3Zr2O12 films at 700 °C and higher. The annealed Li7La3Zr2O12 films have developed surface, which can lead to improved contact between the solid electrolyte and an electrode in an electrochemical cell. Li7La3Zr2O12 films annealed at 800 °C have the highest lithium-ion conductivity values (2.5·10–7 and 1.5·10–5 S·cm–1 at 90 and 215 °С, respectively). The technology of Li7La3Zr2O12 films formation with the thickness of ~23 µm by tape casting was developed.

In the presented study, films from tetragonal Li7La3Zr2O12 were obtained by electrophoretic deposition (EPD) for the first time. To obtain a continuous and homogeneous coating on Ni and Ti substrates, iodine was added to the Li7La3Zr2O12 suspension. The EPD regime was developed to carry out the stable process of deposition. The influence of annealing temperature on phase composition, microstructure, and conductivity of membranes obtained was studied. It was established that the phase transition from tetragonal to low-temperature cubic modification of solid electrolyte was observed after its heat treatment at 400 °C. This phase transition was also confirmed by high-temperature X-ray diffraction analysis of Li7La3Zr2O12 powder. Increasing the annealing temperature leads to the formation of additional phases in the form of fibers and their growth from 32 (dried film) to 104 μm (annealed at 500 °C). The formation of this phase occurred due to the chemical reaction of Li7La3Zr2O12 films obtained by electrophoretic deposition with air components during heat treatment. The total conductivity of Li7La3Zr2O12 films obtained has values of ~10−10 and ~10−7 S cm−1 at 100 and 200 °C, respectively. The method of EPD can be used to obtain solid electrolyte membranes based on Li7La3Zr2O12 for all-solid-state batteries.

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.

Li 7 La 3 Zr 2 O 12 -based compounds are today the most promising solid electrolytes for high-energy lithium and lithium–ion power sources. The solid electrolytes Li 7– x –3 y Al y La 3 Zr 2− x Ta x O 12 ( x = 0.3–0.6, y = 0.05–0.20) were prepared by the sol–gel method. The effect of doping of Li 7 La 3 Zr 2 O 12 in Zr and Li sublattices with tantalum (Ta 5+ ) and aluminum (Al 3+ ) on the crystal structure, morphology, and electrical conductivity of this compound was examined. The compounds obtained had the cubic structure (space group Ia-3d). The resistance of the solid electrolytes obtained was determined by the electrochemical impedance method. The compounds Li 6.25 Al 0.15 La 3 Zr 1.7 Ta 0.3 O 12 , Li 6.3 Al 0.10 La 3 Zr 1.6 Ta 0.4 O 12 , Li 6.2 Al 0.10 La 3 Zr 1.5 Ta 0.5 O 12 , and Li 6.25 Al 0.05 La 3 Zr 1.4 Ta 0.6 O 12 have the maximal lithium-ion conductivity (~2.0 × 10 –4 S cm –1 at 20°C). The heat treatment at 1150°C for 1 h is optimum for forming highly conducting and dense ceramic membranes. Symmetrical cells with Li electrodes show stable behavior in cycling. The solid electrolytes obtained can be used in lithium power sources.