Alkali Metal Systems Research Articles

Basics and Advances of Manganese‐Based Cathode Materials for Aqueous Zinc‐Ion Batteries

It is greatly crucial to develop low‐cost energy storage candidates with high safety and stability to replace alkali metal systems for a sustainable future. Recently, aqueous zinc‐ion batteries (ZIBs) have received tremendous interest owing to their low cost, high safety, wide oxidation states, and sophisticated fabrication process. Nanostructured manganese (Mn)‐based oxides in different polymorphs are the potential cathode materials for the widespread application of ZIBs. However, Mn‐based oxide materials suffer from several drawbacks, such as low electronic/ionic conductivity and poor cycling performance. To overcome these issues, various structural modification strategies have been adopted to enhance their electrochemical activity, including phase/defect engineering, doping with foreign atoms (e.g., metal and/or nonmetal atoms), and coupling with carbon materials or conducting polymers. Herein, this review targets to summarize the advantages and disadvantages of the above‐mentioned strategies to improve the electrochemical performance of the cathodic part of ZIBs. The challenges and suggestions for the development of manganese oxides for ZIBs are put forward.

Syntheses, characterization and theoretical calculation of the first alkali magnesium pyrophosphate fluorides with a short cutoff edge

Two new alkali/alkaline-earth metal pyrophosphate fluorides, A2Mg2P2O7F2 (A = K, Rb) have been synthesized, structurally analyzed, and characterized for the first time. They both crystallize in the Pbcn space group and show similar crystal structures. Their structures contain 1[Mg2O7F3]∞ chains made up of edge-sharing MgO4F2 octahedra and 2[A2O11F4]∞ layers built by face-sharing [A2O11F4] clusters, which are bridged by isolated P2O7 units to construct a 3D framework. It's worth noting that A2Mg2P2O7F2 (A = K, Rb) are the first pyrophosphate fluoride in the A-Mg-P-O-F (A = alkali metal) system. Furthermore, the optical measurements of the title compounds show that they all possess UV absorption cutoff edges. First-principles theoretical studies were conducted to understand the electronic structures.

Mild solvothermal syntheses and crystal structures of two quaternary hetero-transition metal sulfides RbAg5HgS4 and CsAgHgS2

Two quaternary hetero-transition metal sulfides RbAg5HgS4 (1) and CsAgHgS2 (2) have been successfully synthesized under mild solvothermal method in the presence of thiophenol as a mineralizer. Compound 1 features an interesting 3-D [Ag5HgS4]- framework composed of 16-membered ring [Ag (2)4M(1)4S8] (M ​= ​Ag/Hg) and quasi-8-membered ring [Ag (2)4S4] which are all constructed by MS2 and AgS2 linear units. Compound 2 possesses anionic [AgHgS2]nn− layers formed with MS4 (M ​= ​Ag/Hg) tetrahedra, in which Ag+ and Hg2+ ions occupy the same crystallographic site. Particularly, this is the first time that quaternary A-Ag-Hg-S (A ​= ​alkali metal) system were explored via solvothermal method, which demonstrates that structural directing agents have significant influence on the structures of hetero-transition metal sulfides. Furthermore, the XRD experiment and band gap value of compound 2 were also investigated.

Review of Multifunctional Separators: Stabilizing the Cathode and the Anode for Alkali (Li, Na, and K) Metal-Sulfur and Selenium Batteries.

Alkali metal batteries based on lithium, sodium, and potassium anodes and sulfur-based cathodes are regarded as key for next-generation energy storage due to their high theoretical energy and potential cost effectiveness. However, metal-sulfur batteries remain challenged by several factors, including polysulfides' (PSs) dissolution, sluggish sulfur redox kinetics at the cathode, and metallic dendrite growth at the anode. Functional separators and interlayers are an innovative approach to remedying these drawbacks. Here we critically review the state-of-the-art in separators/interlayers for cathode and anode protection, covering the Li-S and the emerging Na-S and K-S systems. The approaches for improving electrochemical performance may be categorized as one or a combination of the following: Immobilization of polysulfides (cathode); catalyzing sulfur redox kinetics (cathode); introduction of protective layers to serve as an artificial solid electrolyte interphase (SEI) (anode); and combined improvement in electrolyte wetting and homogenization of ion flux (anode and cathode). It is demonstrated that while the advances in Li-S are relatively mature, less progress has been made with Na-S and K-S due to the more challenging redox chemistry at the cathode and increased electrochemical instability at the anode. Throughout these sections there is a complementary discussion of functional separators for emerging alkali metal systems based on metal-selenium and the metal-selenium sulfide. The focus then shifts to interlayers and artificial SEI/cathode electrolyte interphase (CEI) layers employed to stabilize solid-state electrolytes (SSEs) in metal-sulfur solid-state batteries (SSBs). The discussion of SSEs focuses on inorganic electrolytes based on Li- and Na-based oxides and sulfides but also touches on some hybrid systems with an inorganic matrix and a minority polymer phase. The review then moves to practical considerations for functional separators, including scaleup issues and Li-S technoeconomics. The review concludes with an outlook section, where we discuss emerging mechanics, spectroscopy, and advanced electron microscopy (e.g. cryo-transmission electron microscopy (cryo-TEM) and cryo-focused ion beam (cryo-FIB))-based approaches for analysis of functional separator structure-battery electrochemical performance interrelations. Throughout the review we identify the outstanding open scientific and technological questions while providing recommendations for future research topics.

Stoner enhancement from interstitial electrons in Y2C toward a spontaneous ferromagnetic electride.

The evolutionary magnetism associated with the interlayer spacing in two-dimensional (2D) Y2C electrides has been investigated by first-principles total-energy calculations based on density functional theory. Several structures with different c-axis parameters around the optimized value were taken into our consideration. Mapping of the electron localization function shows that the interstitial electron is strongly localized at the body center position (denoted as the X-site) in the primitive rhombohedral unit cell, serving as an anion which is ionically bonded with the cationic framework of the Y2C layer. As the c-axis parameter decreases, the volume of the X-site is systematically reduced while both the charge and magnetization density for X are increased. It indicates that the compressed inter-layer space effectively increases the degree of localization of interstitial anionic electrons (IAEs) correlated with their enhanced local magnetic moments. We have found that the exchange splitting of the density of states for Y2C becomes more prominent with a decrease in the c-axis parameter as predicted from a pressurized alkali metal system. Accompanied by the calculated magnetization values, it can be concluded that the increased degree of localization for IAEs between cationic framework layers has greatly influenced the Stoner parameter leading to the increased magnetic moment based on the Stoner enhancement mechanism; hence, it plays a key role in the emergence of a spontaneous ferromagnetic electride.

Dual-frequency cesium spin maser

Co-magnetometers have been validated as valuable components of the atomic physics toolbox in fundamental and applied physics. So far, the explorations have been focused on systems involving nuclear spins. Presented here is a demonstration of an active alkali-metal (electronic) system, i.e. a dual frequency spin maser operating with the collective caesium F=3 and F=4 spins. The experiments have been conducted in both magnetically shielded and unshielded environments. In addition to the discussion of the system's positive feedback mechanism, the implementation of the dual frequency spin maser for industrial non-destructive testing is shown. The stability of the F=3 and F=4 spin precession frequency ratio measurement is limited at the $3 \times 10^{-8}$ level, by the laser frequency drift, corresponding to a frequency stability of 1.2 mHz for $10^4$ sec integration time. We discuss measurement strategies that could improve this stability to nHz, enabling measurements with sensitivities to the axion-nucleon and axion-electron interactions at the levels of $f_a/C_N \sim 10^9$ GeV and $f_a/C_e \sim 10^8$ GeV, respectively.

Ab initioproperties of the NaLi molecule in thea3Σ+electronic state

Ultracold polar and magnetic ${}^{23}$Na${}^6$Li molecules in the rovibrational ground state of the lowest triplet $a^3\Sigma^+$ electronic state have been recently produced. Here, we calculate the electronic and rovibrational structure of these 14-electron molecules with spectroscopic accuracy ($<0.5\,$cm$^{-1}$) using state-of-the-art ab initio methods of quantum chemistry. We employ the hierarchy of the coupled-cluster wave functions and Gaussian basis sets extrapolated to the complete basis set limit. We show that the inclusion of higher-level excitations, core-electron correlation, relativistic, QED, and adiabatic corrections is necessary to reproduce accurately scattering and spectroscopic properties of alkali-metal systems. We obtain the well depth, $D_e=229.9(5)\,$cm$^{-1}$, the dissociation energy, $D_0=208.2(5)\,$cm$^{-1}$, and the scattering length, $a_s=-84^{+25}_{-41}\,$bohr, in good agreement with recent experimental measurements. We predict the permanent electric dipole moment in the rovibrational ground state, $d_0=$0.167(1)$\,$debye. These values are obtained without any adjustment to experimental data, showing that quantum chemistry methods are capable of predicting scattering properties of many-electron systems, provided relatively weak interaction and small reduced mass of the system.

Liquid Metal Diagnostics

Liquid metal (LM) plasma-facing components (PFCs) (LM-PFCs) within next-generation fusion reactors are expected to enhance plasma confinement, facilitate tritium breeding, improve reactor thermal efficiency, and withstand large heat and particle fluxes better than solid components made from tungsten, molybdenum, or graphite. Some LM divertor concepts intended for long-pulse operation at >20 MW/m2 incorporate thin (~1 cm), fast-moving (~5 to 10 m/s), free-surface flows. Such systems will require a range of diagnostics to monitor and control the velocity, flow depth, temperature, and impurity concentration of the LM. This paper will highlight technologies developed for the fission and casting/metallurgical industries that can be adapted to meet the needs of LM-PFC research. This paper is divided into four major parts. The first part will look at noncontact flowmeter technologies that are suitable for high-temperature alkali metal systems. These technologies include rotating Lorentz-force flowmeters for bulk flow rate measurements and particle tracking techniques for surface velocity measurements. Second, this paper will detail the operation of a new inductive level sensor that can be used within free-surface LM-PFCs. This robust level sensor can be mounted below the substrate that supports the LM, so it is simple to install and is protected from the damaging conditions inside a fusion reactor. It has been shown that this level sensor can be calibrated using either numerical or experimental techniques. Third, distributed temperature sensors based on fiber-optic technologies will be discussed. This advanced measurement technique provides temperature data with high spatial resolution and has recently been successfully tested in LM systems. Last, diagnostics to measure impurity concentration, such as electrochemical cells, plugging meters, and spectroscopic systems, will be addressed.

Electrolyte Science for Divalent Metal Batteries

Multivalent cation-based electrochemical energy storage concepts provide great promise and great challenges as beyond Li-ion technologies. Such systems based on Mg2+, Zn2+, or Ca2+ cations challenge current understanding of solvation and resultant properties in non-aqueous electrolytes, where the doubly-charged cation introduces new liquid solvation behavior compared to the more established alkali-metal (Li+, Na+) systems. In this presentation, we drive toward a more unified framework for understanding of solvation phenomena through a systematic comparison of solvation structure and dynamics in organic divalent electrolytes. Connecting these solvation trends to critical ensemble electrolyte properties such as ion transport and electrochemical stability will be the focus of this work. Specifically, we will highlight lessons learned from ethereal solvent systems (cylic ethers and glymes), which are the solvents most commonly employed in beyond Li-ion chemistries at large. We will discuss how the competition between anion and solvent coordination with the divalent cation regulates the observed electrochemical behavior and connect these themes to the principles of electrolyte design.

Surface Properties of Melts of Binary Systems of Alkali Metals

The results of calculations of the surface properties of melts of alkali-metal systems based on experimental surface tension isotherms are presented. It is shown that the authors of the equation of the surface-tension isotherm have described experimental isotherms of the surface tension of binary alkali-metal systems with high accuracy. The results of calculations of the parameters of the surface-tension isotherm β and F, the component adsorption, and the surface composition of the melts of binary alkali-metal systems in approximations of ideal and real solutions are given. Analysis of the results shows that the binary systems Na–K, K–Rb, and Rb–Cs are closer than others to the ideal system. It is noted that one of the determining factors in the adsorption processes of components of binary alkali-metal systems is geometric: the greater is the ionic radius of the added component of the solvent radius, the stronger is the adsorption of the added (second) component of the binary system.

Recognition of Different Metal Cations by a trans‐4‐[4‐(Dimethylamino)styryl]‐1‐methylpyridinium Iodide@Tetramethylcucurbit[6]uril Probe

Based on the study of a known host–guest inclusion complex comprising cucurbit[6]uril (Q[6]) and a hemicyanine dye, trans‐4‐[4‐(dimethylamino)styryl]‐1‐pyridinium iodide (t‐DSMI), a water‐soluble symmetric tetramethylcucurbit[6]uril (TMeQ[6]), was selected to construct a t‐DSMI‐based probe to test the response to various metal cations in neutral water. The experimental results revealed that the probe responded to Cs+ cations in alkali metal systems, Ba2+ and Sr2+ cations in alkaline earth metal systems, Eu3+, Tm3+ and Yb3+ cations in lanthanide systems, and Cr3+, Fe3+ and Hg2+ cations in systems containing transition and other metal cations, via obvious fluorescence quenching.

Broad Feshbach resonances in ultracold alkali-metal systems

A comprehensive search for "broad" Feshbach resonances (FRs) in all possible combinations of stable alkali-metal atoms is carried out, using a multi-channel quantum-defect theory assisted by the analytic wave functions for a long-range van-der-Waals potential. A number of new "broad" $s$-, $p$- and $d$-wave FRs in the lowest-energy scattering channels, which are stable against two-body dipolar spin-flip loss, are predicted and characterized. Our results also show that "broad" FRs of $p$- or $d$-wave type that are free of two-body loss do not exist between fermionic alkali-metal atoms for magnetic field up to 1000\,G. These findings constitute helpful guidance on efforts towards experimental study of high-partial-wave coupling induced many-body physics.

Hydrogen Bonding Assisted Construction of Graphite-like Deep-UV Optical Materials with Two Types of Parallel π-Conjugated Units

Three new formic-borates Na(COOH)[B(OH)3](H2O)2 (1), K3(COOH)3[B(OH)3]2 (2), and (HCOOH)3[B(OH)3]2·3H2O (3), containing two types of planar π-conjugated BO3 and HCOO groups, have been synthesized via systematic investigations in A–HCOO–BO3 (A = alkali metal) systems using hydrothermal methods. Compounds 1 and 2 crystallize in the centrosymmetric space groups Pnma and C2/c, and compound 3 crystallizes in the non-centrosymmetric space groups Pn, respectively. All the three titled compounds exhibited three-dimensional (3-D) frameworks with a parallel arrangement of B(OH)3 and HCOO planar π-conjugated units through hydrogen bonding assisted construction. Particularly, compounds 2 and 3 showed a graphite-like layer structure. In compound 1, the Na(COOH)[B(OH)3] chains are connected with water molecules by hydrogen bonding to form the 3-D framework. In 2, graphite-like {(COOH)3[B(OH)3]2}3– layers composed of HCOO and B(OH)3 groups construct the 3-D framework through the bridging of charge-balance cations K+ loc...

Transformations of cyclohexa-1,4-diene under the action of biphenyl—alkali metal systems in THF. Synergistic acceleration by mixtures of lithium and sodium

In the interaction of cyclohexa-1,4-diene (1,4-CHD) with a mixture of biphenyl and metallic lithium or sodium in THF at 20 °C, three processes occur, viz., disproportionation of 1,4-CHD to form benzene and cyclohexene, dehydrogenation of 1,4-CHD to form benzene and molecular hydrogen, and dehydrogenation of 1,4-CHD to form benzene and lithium or sodium hydride. In the case of lithium on the use of an equimolar amount of biphenyl, the isomerization of 1,4-CHD to cyclohexa-1,3-diene is also observed. When the molar ratio Li(Na): Ph2 increases from 1 : 1 to 2 : 1, i.e., when the reaction is carried out in the presence of an alkali metal solid phase, the overall conversion of 1,4-CHD into benzene and cyclohexene increases. The use of mixtures of lithium and sodium leads to acceleration of the processes of the formation of benzene and cyclohexene. The possible mechanism of the synergistic effect found is discussed.

Electron Solvation in Liquid Ammonia: Lithium, Sodium, Magnesium, and Calcium as Electron Sources.

A free electron in solution, known as a solvated electron, is the smallest possible anion. Alkali and alkaline earth atoms serve as electron donors in solvents that mediate outer-sphere electron transfer. We report herein ab initio molecular dynamics simulations of lithium, sodium, magnesium, and calcium in liquid ammonia at 250 K. By analyzing the electronic properties and the ionic and solvation structures and dynamics, we systematically characterize these metals as electron donors and ammonia molecules as electron acceptors. We show that the solvated metal strongly modifies the properties of its solvation shells and that the observed effect is metal-specific. Specifically, the radius and charge exhibit major impacts. The single solvated electron present in the alkali metal systems is distributed more uniformly among the solvent molecules of each metal's two solvation shells. In contrast, alkaline earth metals favor a less uniform distribution of the electron density. Alkali and alkaline earth atoms are coordinated by four and six NH3 molecules, respectively. The smaller atoms, Li and Mg, are stronger electron donors than Na and Ca. This result is surprising, as smaller atoms in a column of the periodic table have higher ionization potentials. However, it can be explained by stronger electron donor-acceptor interactions between the smaller atoms and the solvent molecules. The structure of the first solvation shell is sharpest for Mg, which has a large charge and a small radius. Solvation is weakest for Na, which has a small charge and a large radius. Weak solvation leads to rapid dynamics, as reflected in the diffusion coefficients of NH3 molecules of the first two solvation shells and the Na atom. The properties of the solvated electrons established in the present study are important for radiation chemistry, synthetic chemistry, condensed-matter charge transfer, and energy sources.

Enhancement of the electrochemical properties with the effect of alkali metal systems on PEO/PVdF-HFP complex polymer electrolytes

Polymer blend electrolytes based on poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) were prepared by using different lithium salts LiX (X = ClO4, BF4, CF3SO3, and N [CF3SO2]2) using solution casting technique. To confirm the structure and complexation of the electrolyte films, the prepared electrolytes were subjected to X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. Alternating current (AC) impedance analysis was performed for all the electrolyte samples at various temperatures from 303 to 343 K. The result suggests that among the various lithium salts, LiN[CF3SO2]2-based electrolytes exhibited the highest ionic conductivity at 8.20 × 10−4 S/cm. The linear variation of the ionic conductivity of the polymer electrolytes with increasing temperature suggests the Arrhenius-type thermally activated process. Activation energies were found to decrease when doping with lithium imide salt. The dielectric behavior has been analyzed using dielectric permittivity (e*), electric modulus (M*), and dissipation factor (tanδ) of the samples. Cyclic voltammetry has been performed for the electrolyte films to study their cyclability and reversibility. Thermogravimetric and differential thermal analysis (TG/DTA) was used to ascertain the thermal stability of the electrolytes, and the porous nature of the electrolytes was identified using scanning electron microscopy via ion hopping conduction. Surface morphology of the sample having maximum conductivity was studied by an atomic force microscope (AFM).

Phase Formation in REE-Containing Water-Salt Systems at the Preparatory Stages of the ulticomponent Oxide Functional Materials Formation

Using a number of physico-chemical methods, the authors have studied the nature and laws of chemical interaction between structural components, heterogeneous equilibrium (25-100 оC) in model triple water-salt systems of sulphates, nitrates, chlorides neodymium and alkali metals. Complicated processes of complex formation in creations the entire classes of anionic Ln3+ complexes have been determined. Polythermal solubility diagrams have been built for the studied systems. Conditions for the source materials and new phase existence are clarified. Optimal growth conditions have been determined, and synthesis of single-crystal samples has been carried out. A number of physical and chemical properties are studied, and the individuality of double salts has been confirmed. A number of features and usage patterns were revealed in transformations. The obtained results are treated as a reliable scientific basis for substantiation of preparatory process in the up-to-date REE-containing functional materials production. Keywords: Alkali metals, chlorides, neodymium, nitrates, sulfates, water-salt systems.

Orbital Feshbach Resonance in Alkali-Earth Atoms.

For a mixture of alkali-earth atomic gas in the long-lived excited state ^{3}P_{0} and the ground state ^{1}S_{0}, in addition to nuclear spin, another "orbital" index is introduced to distinguish these two internal states. In this Letter we propose a mechanism to induce Feshbach resonance between two atoms with different orbital and nuclear spin quantum numbers. Two essential ingredients are the interorbital spin-exchange process and orbital dependence of the Landé g factors. Here the orbital degrees of freedom plays a similar role as the electron spin degree of freedom in magnetic Feshbach resonance in alkali-metal atoms. This resonance is particularly accessible for the ^{173}Yb system. The BCS-BEC crossover in this system requires two fermion pairing order parameters, and displays a significant difference compared to that in an alkali-metal system.

Ab initiointeraction potentials and scattering lengths for ultracold mixtures of metastable helium and alkali-metal atoms

We have obtained accurate ab initio quartet potentials for the diatomic metastable triplet helium + alkali-metal (Li, Na, K, Rb) systems, using all-electron restricted open-shell coupled cluster singles and doubles with noniterative triples corrections [CCSD(T)] calculations and accurate calculations of the long-range $C_6$ coefficients. These potentials provide accurate ab initio quartet scattering lengths, which for these many-electron systems is possible, because of the small reduced masses and shallow potentials that results in a small amount of bound states. Our results are relevant for ultracold metastable triplet helium + alkali-metal mixture experiments.

KSi2P3: A new layered phosphidopolysilicate (IV)

Abstract A new ternary phosphidopolysilicate (IV), KSi2P3, has been synthesized by high temperature solid state reaction. The compound crystallizes in a new structure type in the monoclinic space group C2/c with a=10.1327(5) A, b=10.1382(5) A, c=21.1181(10) A, β=96.88(0)°, and Z=8. In the structure, all SiP4 tetrahedra are connected with each other by corner-sharing P atoms to form [ Si 2 P 3 ] − ∞ 2 layers, which are stacked along c direction and separated by K+ cations. The two-dimensional structure of KSi2P3 contrasts with those of the two known members in the ternary A/Si/P (A=alkali metal) system, namely Na5SiP3 (zero-dimensional) and K2SiP2 (one-dimensional), which contains less amount of Si. The band gap deduced from UV–vis–IR diffuse reflectance spectrum is 1.72 eV.