Superionic Solid Electrolyte Li7La3Zr2O12 Synthesis and Thermodynamics for Application in All-Solid-State Lithium-Ion Batteries

Li7La3Zr2O12Solid-state reaction was used for Li7La3Zr2O12 material synthesis from Li2CO3, La2O3 and ZrO2 powders. Phase investigation by XRD, SEM and EDS methods of Li7La3Zr2O12 were carried out. The molar heat capacity of Li7La3Zr2O12 at constant pressure in the temperature range 298-800 K should be calculated as Cp,m = 518.135+0.599 × T - 8.339 × T−2, where T is absolute temperature, . Thermodynamic characteristics of Li7La3Zr2O12 were determined as next: entropy S0298 = 362.3 J mol-1 K-1, molar enthalpy of dissolution ΔdHLlZO = ˗ 1471.73 ± 29.39 kJ mol−1, the standard enthalpy of formation from elements ΔfH0 = ˗ 9327.65 ± 7.9 kJ mol−1, the standard Gibbs free energy of formation ∆f G0298 = ˗9435.6 kJ mol-1.

Synthesis Method and Thermodynamic Characteristics of Anode Material Li3FeN2 for Application in Lithium-Ion Batteries

Li3FeN2 material was synthesized by the two-step solid-state method from Li3N (adiabatic camera) and FeN2 (tube furnace) powders. Phase investigation of Li3N, FeN2, and Li3FeN2 was carried out. The discharge capacity of Li3FeN2 is 343 mAh g−1, which is about 44.7% of the theoretic capacity. The ternary nitride Li3FeN2 molar heat capacity is calculated using the formula Cp,m = 77.831 + 0.130 × T − 6289 × T−2, (T is absolute temperature, temperature range is 298–900 K, pressure is constant). The thermodynamic characteristics of Li3FeN2 have the following values: entropy S0298 = 116.2 J mol−1 K−1, molar enthalpy of dissolution ΔdHLFN = −206.537 ± 2.8 kJ mol−1, the standard enthalpy of formation ΔfH0 = −291.331 ± 5.7 kJ mol−1, entropy S0298 = 113.2 J mol−1 K−1 (Neumann–Kopp rule) and 116.2 J mol−1 K−1 (W. Herz rule), the standard Gibbs free energy of formation ΔfG0298 = −276.7 kJ mol−1.

Synthesis Method and Thermodynamic Characteristics of Anode Material Li3FeN2 for Application in Lithium-Ion Batteries

Li3FeN2 material was synthesized by two-step solid-state method from Li3N (adiabatic camera) and FeN2 (tube furnace) powders. Phase investigation of Li3N, FeN2 and Li3FeN2 were carried out. Discharge capacity of Li3FeN2 is 343 mAh g-1, that is about 44.7% of theoretic capacity. The molar heat capacity of Li3FeN2 at constant pressure in the temperature range 298-900 K should be calculated as Cp,m = 77,831 + 0,130 × T – 6,289 × T-2, where T is absolute temperature, . Thermodynamic characteristics of Li3FeN2 were determined as next: entropy S0298 = 116.2 J mol-1 K-1, molar enthalpy of dissolution ΔdHLFN = ˗ 206,537 ± 2,8 kJ mol−1, the standard enthalpy of formation ΔfH0 = ˗ 291.331 ± 5.7 kJ mol−1, entropy S0298 = 113.2 J mol-1 K-1 (Neumann-Kopp rule) and 116.2 J mol-1 K-1 (W.Herz rule), the standard Gibbs free energy of formation ∆f G0298 = ˗276,7 kJ mol-1.

Thermodynamics of nitrogen solutions in liquid nickel

The simplest model of the structure and interatomic interaction is applied to nitrogen solutions in liquid alloys of Fe – Ni system, which earlier (2019) was used by the authors for nitrogen solutions in alloys of Fe – Cr system. The principles of statistical mechanics are used in this model. Thus, three formulas were obtained. The first formula expresses the Sieverts law constant for the solubility of nitrogen in liquid nickel through a similar constant for the solubility of nitrogen in liquid iron and the Wagner interaction coefficient of nitrogen with nickel in low-concentration liquid iron-base alloys. The second formula expresses the partial enthalpy of dissolution of nitrogen in liquid nickel during the formation of an infinitely dilute solution through a similar value for dissolution of nitrogen in liquid iron and the Wagner interaction coefficient of nitrogen with nickel in iron-base liquid alloys. The third formula expresses the Wagner interaction coefficient of nitrogen with iron in low-concentration liquid nickel-base alloys through the Wagner interaction coefficient of nitrogen with nickel in liquid iron-base alloys. The constant of the Sieverts law for the solubility of nitrogen in liquid iron at T = 1873 K is assumed to be 0.044 mass. %. The partial enthalpy of dissolution of nitrogen in liquid iron assumed to be 5.0 kJ/mol. For Wagner interaction coefficient of nitrogen with nickel in iron-base liquid alloys at 1873 K three variants of values were studied: 2.4, 2.6, and 2.85. For the first option, theoretical value of the Sieverts law constant for solubility of nitrogen in liquid nickel at T = 1873 K, equal to 0.00195 mass. % was obtained. Theoretical value of the enthalpy of dissolution of nitrogen in liquid nickel is 52.7 kJ/mol. Theoretical value of the Wagner interaction coefficient of nitrogen with iron in nickel-base liquid alloys is –4.0. The agreement of theory with experiment seems to be satisfactory.

STANDARD ENTHALPY OF FORMATION OF PARAOXYPHENYLGLYCINE AND PRODUCTS OF ITS DISSOCIATION IN AQUEOUS SOLUTION

Depending on the chemical nature of the side radicals, amino acids can be divided into aromatic and aliphatic, as well as amino acids, the presence of non-polar or polar functional groups in the side radicals. Since the characteristics of individual amino acids in the protein are determined by the nature (physico-chemical properties) of their side radicals, which are in a hydrated state. It is also extremely important to study the thermodynamic characteristics of the hydration of the side radicals of amino acids of different chemical nature. To obtain empirical correlations that would establish a connection between the thermodynamic parameters of the interaction of dissolved compounds with the solvent and the size of the molecules to be dissolved (having different physico-chemical nature), it is necessary to accumulate a sufficient amount of experimental data on the heats of dissolution of amino acids. This will allow you to calculate the contribution of intermolecular interactions for different groups of molecules. By potentiometric method the protolytic equilibria in aqueous solutions of paraoxyphenylglycine were investigated. The measurements were carried out at a temperature of 298.15 K and an ionic strength of 0.25 (against the background of potassium nitrate). Calorimetric measurements were carried out on an ampoule calorimeter, with an isothermal shell, a thermistor temperature sensor KMT-14, and an automatic record of the temperature-time curve. The operation of the unit was verified by the integral enthalpy of dissolution in water of crystalline potassium chloride. The agreement between the experimental enthalpies of dissolution of KCl (cr) with the most reliable literature data indicates that there are no systematic errors in the calorimetric system. Samples of para-oxyphenylglycine were weighed on a VLP-200 scale with an accuracy of 2∙10-4 g. The confidence interval of the mean value of ΔH was calculated with a probability of 0.95. A paraxyphenylglycine preparation, «Reachim», was used in the work. The reagent was used without further purification. The RRSU program was used to determine the equilibrium composition of the solutions. Standard enthalpies of combustion and formation of crystalline paraxyphenylglycine were calculated. Thermal effects of dissolution of crystalline paraxyphenylglycine in water and in solutions of potassium hydroxide at 298.15 K were determined with the direct calorimetric method. Standard enthalpies of formation of amino acids and products of their dissociation in aqueous solution were calculated.

Thermodynamic description of U(VI) solubility and hydrolysis in dilute to concentrated NaCl solutions at T = 25, 55 and 80 °C

The solubility and hydrolysis of U(VI) were investigated in 0.10–5.6 m NaCl solutions with 4 ≤ pHm ≤ 14.3 (pHm = −log [H+]) at T = 25, 55 and 80 °C. Batch experiments were conducted under Ar atmosphere in the absence of carbonate. Solubility was studied from undersaturation conditions using UO3 · 2H2O(cr) and Na2U2O7 · H2O(cr) solid phases, equilibrated in acidic (4 ≤ pHm ≤ 6) and alkaline (8.2 ≤ pHm ≤ 14.3) NaCl solutions, respectively. Solid phases were previously tempered in solution at T = 80 °C to avoid changes in the crystallinity of the solid phase in the course of the solubility experiments. Starting materials and solid phases isolated at the end of the solubility experiments were characterized by powder XRD, SEM-EDS, TRLFS and quantitative chemical analysis. The enthalpy of dissolution of Na2U2O7 · H2O(cr) at 25–80 °C was measured independently by means of solution-drop calorimetry. Solid phase characterization indicates the transformation of UO3 · 2H2O(cr) into a sodium uranate-like phase with a molar ratio Na:U ≈ 0.4–0.5 in acidic solutions with [NaCl] ≥ 0.51 m at T = 80 °C. In contrast, Na2U2O7 · H2O(cr) equilibrated in alkaline NaCl solutions remains unaltered within the investigated pHm, NaCl concentration and temperature range. The solubility of Na2U2O7 · H2O(cr) in the alkaline pHm-range is noticeably enhanced at T = 55 and 80 °C relative to T = 25 °C. Combined results from solubility and calorimetric experiments indicate that this effect results from the increased acidity of water at elevated temperature, together with an enhanced hydrolysis of U(VI) and a minor contribution due to a decreased stability of Na2U2O7 · H2O(cr) under these experimental conditions. A thermodynamic model describing the solubility and hydrolysis equilibria of U(VI) in alkaline solutions at T = 25–80 °C is developed, including $\log^* {\rm K}_{\rm s,0}^{\circ} \ \{{\rm Na}_{2}{\rm U}_{2}{\rm O}_{7} \cdot {\rm H}_{2}{\rm O}({\rm cr})\}, \log^{*} \beta _{1,4}^{\circ} $ and related reaction enthalpies. The standard free energy and enthalpy of formation of Na2U2O7 · H2O(cr) calculated from these data are also provided. These data can be implemented in thermodynamic databases and allow accurate solubility and speciation calculations for U(VI) in dilute to concentrated alkaline NaCl solutions in the temperature range T = 25–80 °C.