Alkali Metal Alloys Research Articles

Unveiling dendrite-suppressing potential of alkali metal-based alloys in lithium metal batteries

We reveal a concept of adding K and Na to dual-cation systems and investigate their effects on dendrite growth morphology and electrolyte decomposition reactivity in lithium metal batteries (LMBs). We analyze the effects of Li/K- and Li/Na-alloyed surfaces on Li ion diffusion along the deposition direction, as well as the reactivity of the electrolytes and the composition of the solid electrolyte interface (SEI) resulting from electrolyte decomposition. Compared with the Li/K system, the Li/Na-alloyed surface can significantly reduce Li diffusion along the z-direction and effectively prevent the formation of dendrite-like morphologies. Furthermore, the Li/Na-alloyed surface substantially mitigates the reactivity of the bis(fluorosulfonyl)imide (FSI−) anion and fluorinated ether (TTE) solvent, thus inhibiting the generation of excessive SEI species. Additionally, the regulated and simplified components of a hybrid LiF/NaF SEI layer in the Li/Na system are observed. This hybrid layer is expected to promote the uniform deposition of Li and exhibit excellent electrical insulating properties, thereby effectively preventing electron transfer to the electrolytes and enhancing the Coulombic efficiency of LMBs. This study presents new insights into the dendrite-suppressing potential of alkali-metal alloys for improving the stability and safety of LMBs.

Pressure Stabilized Lithium-Aluminum Compounds with Both Superconducting and Superionic Behaviors

Superconducting and superionic behaviors have physically intriguing dynamic properties of electrons and ions, respectively, both of which are conceptually important and have great potential for practical applications. Whether these two phenomena can appear in the same system is an interesting and important question. Here, using crystal structure predictions and first-principle calculations combined with machine learning, we identify several stable Li-Al compounds with electride behavior under high pressure, and we find that the electronic density of states of some of the compounds has characteristics of the two-dimensional electron gas. Among them, we estimate that Li_{6}Al at 150GPa has a superconducting transition temperature of around 29K and enters a superionic state at a high temperature and wide pressure range. The diffusion in Li_{6}Al is found to be affected by an electride and attributed to the atomic collective motion. Our results indicate that alkali metal alloys can be effective platforms to study the abundant physical properties and their manipulation with pressure and temperature.

Ab initio free energies of liquid metal alloys: Application to the phase diagrams of Li-Na and K-Na

Comparison of free energies between different phases and different compositions underlies the prediction of alloy phase diagrams. To allow direct comparison, consistent reference points for the energies or enthalpies are required, and the entropy must be placed on an absolute scale, yielding absolute free energies. Here we derive absolute free energies of liquids from ab initio molecular dynamics by combining the directly simulated enthalpies with an entropy derived from simulated densities and pair correlation functions. As an example of the power of this method we calculate the phase diagrams of two binary alkali metal alloys, Li-Na and K-Na, revealing a critical point and liquid-liquid phase separation in the former case, and a deep eutectic in the latter. Good agreement with experimental data demonstrates the power of this simple method.

The interdiffusion in liquid alloys of alkali metals with lead

The mutual diffusion in liquid cesium-lead alloys containing from 20 to 70 at.% Pb is investigated by a gamma-ray attenuation technique. The obtained data are compared with the results of similar studies for Li-Pb, Na-Pb, and K-Pb melts, carried out by us earlier. The concentration dependences of the interdiffusion coefficient for alkali-lead liquid systems demonstrate pronounced maxima in the vicinity of 20 or 50 at.% Pb. These phenomena confirm a tendency for chemical short-range ordering in liquid alloys.

State of the Art in Control of Inclusions and Microalloying Elements in Tire Cord Steel and Saw Wire Steel

The extremely thin diameter of steel tire cord wire and steel saw wire are about 80 and 50 μm, respectively. It is supposed that this kind of ultrafine steel wire is easy to break due to large and hard nonmetallic inclusions in the steel during the drawing and standing process. This paper reviews the research advances on inclusion and microalloying elements control in tire cord steel and saw wire steel in the past 20 years. Including: 1) calculation of thermodynamics of inclusion formation in quaternary system; 2) effects of alkali metal alloys and its oxides on inclusions; 3) control of Ti‐containing inclusion and SiO2‐MnO‐Al2O3 inclusion; 4) effect of rare earth on inclusions in saw wire steel; 5) the behavior of inclusions at the solidification front of liquid steel; 6) the effect of inclusion size and morphology on the fracture behavior of steel wire; 7) ultrasonic technology was used to remove inclusions in cord steel; 8) the effect of C, Cr, Co, Ce and V on microstructure and properties of tire cord steel and saw wire steel. Finally, this paper summarizes twelve key problems that should be studied in the next decade to provide reference for metallurgical workers.

Computation of thermophysical properties of liquid metals and alloys on the basis of generalized version of hole theory

• Modification of Frenkel’s hole theory has been applied to liquid metals and alloys. • Liquid metals Na, K, Rb, Cs, Sn and Pb and four alloys K-Rb, Na-Cs, Sn-Pb and Na-K. • Various expressions for r h ,V h , α, β T , P int , E h , ∆E V , ced, α vdw and u were derived. • Interaction study of alkali metal alloys with the help of hole theory. • The calculated and experimental values show excellent. A generalized version of hole theory, recently developed as a modification of Frenkel’s hole theory has been applied successfully, for the first time, to six pure liquid metals (K, Rb, Na, Cs, Pb and Sn) and four liquid metal alloys (K-Rb, Na-Cs, Sn-Pb and Na-K) at different temperatures. Various expressions for r h ,V h , α, β T , P int , E h , ΔE V , ced, α vdw and u were derived for the pure liquid metals and alloys. The calculated and experimental values show excellent agreement demonstrating the success of the theory to the pure liquid metals and alloys.

Mixed alkali-ion transport and storage in atomic-disordered honeycomb layered NaKNi2TeO6

Honeycomb layered oxides constitute an emerging class of materials that show interesting physicochemical and electrochemical properties. However, the development of these materials is still limited. Here, we report the combined use of alkali atoms (Na and K) to produce a mixed-alkali honeycomb layered oxide material, namely, NaKNi2TeO6. Via transmission electron microscopy measurements, we reveal the local atomic structural disorders characterised by aperiodic stacking and incoherency in the alternating arrangement of Na and K atoms. We also investigate the possibility of mixed electrochemical transport and storage of Na+ and K+ ions in NaKNi2TeO6. In particular, we report an average discharge cell voltage of about 4 V and a specific capacity of around 80 mAh g–1 at low specific currents (i.e., < 10 mA g–1) when a NaKNi2TeO6-based positive electrode is combined with a room-temperature NaK liquid alloy negative electrode using an ionic liquid-based electrolyte solution. These results represent a step towards the use of tailored cathode active materials for “dendrite-free” electrochemical energy storage systems exploiting room-temperature liquid alkali metal alloy materials.

Decoupling Electrolyte and Electrode Reactions Using in-Operando Electrochemical X-Ray Powder Diffraction

Lithium-ion batteries are the dominant energy storage technology – steady and significant progress toward lower costs, better safety, and better performance is being realized by an improved understanding and control of new materials and system engineering. Various novel materials for lithium and lithium-ion battery electrodes are emerging, many of which depend on alkali-metal alloys. Among them, Aluminum electrodes offer the potential for high lithium-ion capacities at low costs, for example, capacities of 2000 mAh/g (six times higher than graphite, the current commercial standard) can be accessed at moderate temperatures (above 40°C),1 and recent studies show that Aluminum foil electrodes can act as both the active material and current collector.2 Nevertheless, challenges with capacity fade, electrolyte breakdown, slow diffusion and nucleation barriers still exist and alkali-metal electrochemical reactivity is not fully understood. Elevated temperature operation can be used to overcome nucleation barriers and slow diffusion, but at the cost of increased rates of liquid electrolyte breakdown. Here, we combine controlled temperature electrochemical lithiation and delithiation with x-ray powder diffraction for in-situ studies of electrode and electrolyte reactions to shed light on these problems.Our in-operando cell is based on commercially available ultra-high vacuum compatible Conflat flanges with Beryllium windows and electrical feedthroughs to maintain commercially-relevant stack pressure and cell sealing.3 We will report on cell design and mechanical, electrochemical, and x-ray diffraction performance, including full-powder-pattern refinement of the Li-Al electrode material during electrochemical lithiation and delithiation. Such refinement of the diffraction patterns allows us to quantify the fractions of the phases formed as well as details of the crystal structure (e.g. solid solution vs. new phase). The evolution of the measured cell potential (red line) and the powder diffraction pattern (heat map) are shown in sections a) and b), respectively, of the attached figure. We confirm the formation of AlLi, Al2Li3 and AlLi2 and follow their fractions in-operando during charge and discharge of the cell. In section a) of the attached figure, electrode composition determined from pattern refinement (black dots) is compared to the composition predicted from electrochemical methods (blue solid lines) to separate the effects of electrode phase transitions and electrolyte breakdown. Electrode composition determined from XRD matches well the predicted composition at the beginning of the lithiation process, however it starts to deviate significantly by the time the delithiation is finished. In-operando XRD allows us to quantify this deviation and calculate the rate of liquid electrolyte breakdown. Better understanding of phase formation and electrolyte breakdown in Li-ion battery electrode materials and electrolytes will enable more robust production and improved performance of the batteries on the market.[1] M.Z. Ghavidel et al., Journal of The Electrochemical Society, 166 (16) A4034-A4040 (2019).[2] H. Li et al., Nature Communications, 11, 1584 (2020).[3] M.D. Fleischauer et al, Journal of The Electrochemical Society, 166 (2) A398-A402 (2019). Figure 1

A Ternary Hybrid-Cation Room-Temperature Liquid Metal Battery and Interfacial Selection Mechanism Study.

The dendrite-free sodium-potassium (Na-K) liquid alloy composed of two alkali metals is one of the ideal alternatives for Li metal as an anode material while maintaining large capacity, low potential, and high abundance. However, Na- or K-ion batteries have limited cathode materials that can deliver stably large capacity. Combining advantages of both, a hybrid-cation liquid metal battery is designed for a Li-ion-insertion-based cathode to deliver stable high capacity using a Na-K liquid anode to avoid dendrites. The mechanical property of the Na-K alloy is confirmed by simulation and experimental characterization, which leads to stable cycling performance. The charge carrier selection principle in this ternary hybrid-cation system is investigated, showing consistency with the proposed interfacial layer formation and ion distribution mechanism for the electrochemical process as well as the good stability. With Li ions contributing stable cycling as the cathode charge carrier, the K ion working as charge carrier on the anode, and Na as the medium to liquefy K metal, such a ternary hybrid battery system not only inherits the rich battery chemistry of Li-insertion cathodes but also broadens the understanding of alkali metal alloys and hybrid-ion battery chemistry.

Erratum

Erratum to the paper “The heat capacity at constant pressure in the nearly-free-electron approximation for binary liquid alloys of alkali metals” (HTHP, 2018, v. 47, p. 205-211)

Mutual diffusion in liquid alloys of heavy alkali metals with bismuth

Interdiffusion coefficients for liquid cesium–bismuth alloys containing from 20 to 40 at. % Bi are measured using a gamma-ray attenuation technique. The obtained results are compared with the data on mutual diffusion in the rubidium–bismuth melts studied earlier. The comparison shows that the concentration dependences of the interdiffusion coefficient for Rb–Bi and Cs–Bi liquid systems demonstrate common features, namely, pronounced maxima at certain compositions. The origin of these features is briefly discussed.

The Variational Calculation of Bulk Moduli for Liquid Binary Alloys of Alkali Metals. Acta Physica Polonica A 131, 237 (2019), ERRATUM

The Variational Calculation of Bulk Moduli for Liquid Binary Alloys of Alkali Metals. Acta Physica Polonica A 131, 237 (2019), ERRATUM

Square-well self-diffusion coefficients in liquid binary alloys of alkali metals within the mean spherical approximation

The concentration dependencies of the self-diffusion coefficients in liquid Na–K and K–Cs alloys at T = 373 K are calculated in the framework of the linear trajectory approximation in conjunction with the square-well (SW) model treated by the mean spherical approximation in the semi-analytical representation. It is shown that this approach allows to achieve a good description of diffusion properties for liquid binary metal alloys at the same values of the SW parameters that lead to a good description of the structure and entropy for alloys under consideration.

Addendum to the erratum to the paper “Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys” (J. Non-Cryst. Sol., 429 (2015), p. 234)

Addendum to the erratum to the paper “Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys” (J. Non-Cryst. Sol., 429 (2015), p. 234)

The Variational Calculation of Bulk Moduli for Liquid Binary Alloys of Alkali Metals

The Variational Calculation of Bulk Moduli for Liquid Binary Alloys of Alkali Metals

A generalized model on the evaluation of entropy and entropy of mixing of liquid Na-Sn alloys

Recently proposed theory of entropy of mixing of the structurally inhomogeneous binary liquid alloys of alkali metals and group-IV elements is applied successfully to the liquid Na-Sn alloy. This alloy indicates chemical short range ordering (CSRO) i.e. exhibits partially salt like characteristics due to strong tendencies to compound formation, in the solid as well as in the liquid state. So, the generalized model for entropy of charged-hard-spheres mixture of arbitrary charge and size is employed to evaluate entropies of mixing, treating the sample as partially charge transfer system. The computed entropies of mixing are in excellent agreement with the experimental data.

Erratum to the paper “Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys” [J. Non-Cryst. Solids 401 (2014) p. 101–104

Erratum to the paper “Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys” [J. Non-Cryst. Solids 401 (2014) p. 101–104

ChemInform Abstract: Facile and Efficient Exfoliation of Inorganic Layered Materials Using Liquid Alkali Metal Alloys.

AbstractSingle‐ and few‐layer MoS2, WS2, and BN nanosheets are prepared through intercalation and exfoliation using liquid NaK or NaLi alkali metal alloys in DME at room temperature for 24—48 h.

Facile and efficient exfoliation of inorganic layered materials using liquid alkali metal alloys.

A facile and efficient exfoliation process has been reported to produce single- and few-layer nanosheets of MoS2, WS2 and BN using liquid alloys of alkali metals at room temperature. The colloidal dispersions of MoS2 and WS2 layers were highly stable over several months, which allowed us to easily prepare films of MoS2 and WS2 by vacuum filtration or spraying.

Binary Alloy Clusters: Structures and Electronic Properties

Synthesis, characterization, physics, and chemistry of nanoclusters have been the focus of intense attention for the last two decades. Also, their unique statues that they are between molecule and bulk material is the central reason for the theoretical researcher to understand the transition from atom to cluster/molecule and then to solid state. In this review we restrict ourselves to the recent advances in the structural and electronic properties of binary alloy clusters. This type of clusters is particularly of importance thanks to their very availability for being tuned, by changing their sizes, according to any special needs. A brief summary of the classification of clusters as well as the experimental techniques and theoretical methods to study them, and the possible applications of alloy clusters are given in the introduction part. Several binary alloy cluster types, including semiconductor, alkali and transition metal, oxide, and ionic binary alloy clusters, are widely reviewed considering extensively the most recent articles.