Low-grade heat (below 373 K) is abundant and ubiquitous, but mostly wasted due to the lack of cost-effective recovery technologies. The liquid-state thermocell (LTC), an inexpensive and scalable thermoelectric device, may be commercially viable for harvesting low-grade heat energy if its Carnot-relative efficiency (ηr) reaches ~5%, which is a challenging metric to achieve experimentally. We used a thermosensitive crystallization and dissolution process to induce persistent concentration gradient of redox ions, a highly enhanced Seebeck coefficient (~3.73 mV K–1), and suppressed thermal conductivity in LTCs. As a result, we achieved a high ηr of 11% for LTCs near room temperature, and a substantially decreased cost-performance of our LTC. Our device demonstration offers promise for cost-effective low-grade heat harvesting.

https://science.sciencemag.org/content/sci/370/6514/342.full.pdf

Thermosensitive crystallization-boosted liquid thermocells for low-grade heat harvesting.

Systematic review of lithium extraction from salt-lake brines via precipitation approaches

Aqueous lithium-ion batteries

This paper is part of a series of studies on the development of a multi-temperature thermodynamically consistent model for salt lake brine systems. Under the comprehensive thermodynamic framework proposed in our previous study, the thermodynamic and phase equilibria properties of the sulfate binary systems (i.e., Li2SO4 + H2O, Na2SO4 + H2O, K2SO4 + H2O, MgSO4 + H2O and CaSO4 + H2O) were simulated using the Pitzer-Simonson-Clegg (PSC) model. Various type of thermodynamic properties (i.e., water activity, osmotic coefficient, mean ionic activity coefficient, enthalpy of dilution and solution, relative apparent molar enthalpy, heat capacity of aqueous phase and solid phases) were collected and fitted to the model equations. The thermodynamic properties of these systems can be well reproduced or predicted using the obtained model parameters. Comparisons with the experimental or model values in literature indicate that the model parameters determined in this study can describe all of the thermodynamic and phase equilibria properties of these binary sulfate systems from infinite dilution to saturation and freezing point temperature to approx. 500 K.

Phase diagrams and thermochemical modeling of salt lake brine systems. III. Li2SO4+H2O, Na2SO4+H2O, K2SO4+H2O, MgSO4+H2O and CaSO4+H2O systems

We systematically studied the ability of 20 alkali halides to form solid hydrates in the frozen state from their aqueous solutions by terahertz time-domain spectroscopy combined with density functional theory (DFT) calculations. We experimentally observed the rise of new terahertz absorption peaks in the spectral range of 0.3-3.5 THz in frozen alkali halide solutions. The DFT calculations prove that the rise of observed new peaks in solutions containing Li+, Na+, or F- ions indicates the formation of salt hydrates, while that in other alkali halide solutions is caused by the splitting phonon modes of the imperfectly crystallized salts in ice. As a simple empirical rule, the correlation between the terahertz signatures and the ability of 20 alkali halides to form a hydrate has been established.

Terahertz Signatures of Hydrate Formation in Alkali Halide Solutions

The solubility data for lithium sulfate and its double salts in water are reviewed. Where appropriate, binary, ternary, and multicomponent systems are critically evaluated. The best values were selected on basis of these evaluations and presented in tabular form. Fitting equations and plots are provided. The quantities, units, and symbols used are in accord with IUPAC recommendations. The original data have been reported and, if necessary, transferred into the units and symbols recommended by IUPAC. The literature on solubility data is covered up to the end of 2015.

IUPAC-NIST Solubility Data Series. 104. Lithium Sulfate and its Double Salts in Aqueous Solutions

For lithium halides, LiX (X = Cl, Br and I), hydrates with a water content of 1, 2, 3 and 5 moles of water per formula unit are known as phases in aqueous solid-liquid equilibria. The crystal structures of the monohydrates of LiCl and LiBr are known, but no crystal structures have been reported so far for the higher hydrates, apart from LiI·3H2O. In this study, the crystal structures of the di- and trihydrates of lithium chloride, lithium bromide and lithium iodide, and the pentahydrates of lithium chloride and lithium bromide have been determined. In each hydrate, the lithium cation is coordinated octahedrally. The dihydrates crystallize in the NaCl·2H2O or NaI·2H2O type structure. Surprisingly, in the tri- and pentahydrates of LiCl and LiBr, one water molecule per Li+ ion remains uncoordinated. For LiI·3H2O, the LiClO4·3H2O structure type was confirmed and the H-atom positions have been fixed. The hydrogen-bond networks in the various structures are discussed in detail. Contrary to the monohydrates, the structures of the higher hydrates show no disorder.

Higher hydrates of lithium chloride, lithium bromide and lithium iodide.

Abstract For the ternary systems, Rb 2 SO 4 – CaSO 4 – H 2 O and Cs 2 SO 4 – CaSO 4 – H 2 O, solubility data have been determined at ambient temperatures (22 and 25 °C). In both systems, gypsum is found as the stable CaSO 4 -phase in the presence of low alkali metal sulfate concentrations. In addition, two double salts exist in the Rb-system: Rb-disalt (Rb 2 SO 4 ·2CaSO 4 ) and Rb-syngenite (Rb 2 SO 4 ·CaSO 4 ·H 2 O) in addition to gypsum and Rb 2 SO 4 . For Rb-syngenite, the crystal structure was determined by single crystal structure analysis (space group P 21/ m (11), a = 6.323 Å, b = 7.223 Å, c = 10.044 Å, β = 102.96°, Z = 2, V = 447.03 Å 3 ), which is isomorphous to potassium syngenite (K 2 SO 4 ·CaSO 4 ·H 2 O). In the Cs-system, besides gypsum and Cs 2 SO 4 , only the double salt Cs 2 SO 4 ·2CaSO 4 exists. Graphical abstract 

/pdf/solubility-equilibria-in-the-ternary-systems-rb2so4-caso4-3u4khf8d.pdf

Solubility equilibria in the ternary systems Rb2SO4 – CaSO4 – H2O and Cs2SO4 – CaSO4 – H2O at ambient temperature, and the crystal structure of rubidium syngenite

. Part of the process to ensure the safety of radioactive waste disposal is the
predictive modeling of the solubility of all relevant toxic components in a
complex aqueous solution. To ensure the reliability of thermodynamic
equilibrium modeling as well as to facilitate the comparison of such
calculations done by different institutions, it is necessary to create a
mutually accepted thermodynamic reference database. To meet this demand
several institutions in Germany joined efforts and created THEREDA (Moog et
al., 2015). THEREDA is a suite of programs at the base of which resides a relational
databank. Special emphasis is put on thermodynamic data along with suitable
Pitzer coefficients, which enable the calculation of solubilities in
high-saline solutions. Registered users may either download single
thermodynamic data or ready-to-use parameter files for the geochemical
speciation codes PHREEQC, Geochemist's Workbench, CHEMAPP, or TOUGHREACT. Data
can also be downloaded in a generic JSON format to enable the import into
other codes. The database can be accessed via the world wide web:
 http://www.thereda.de (last access: 1 November 2021). Prior to release, the released part of the database is subjected to many
tests. Results are compared to results from earlier releases and among the
different codes. This is to ensure that by additions of new and modification
of existing data no adverse side effects on calculations are
caused. Furthermore, our website offers an increasing number of examples for
applications, including graphical representation, which can be filtered by
components of the calculated system.

/pdf/thereda-thermodynamic-reference-database-ep4ygjj8s9.pdf

Julia Sohr

Papers

IUPAC-NIST Solubility Data Series. 104. Lithium Sulfate and its Double Salts in Aqueous Solutions

Higher hydrates of lithium chloride, lithium bromide and lithium iodide.

Solubility equilibria in the ternary systems Rb2SO4 – CaSO4 – H2O and Cs2SO4 – CaSO4 – H2O at ambient temperature, and the crystal structure of rubidium syngenite

THEREDA – Thermodynamic Reference Database