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Recently, a disruptive idea was reported about the discovery of a new type of battery named Liquid Displacement Battery (LDB) comprising liquid metal electrodes and molten salt electrolyte. This cell featured a novel concept of a porous electronically conductive faradaic membrane instead of the traditional ion-selective ceramic membrane. LDBs are attractive for stationary storage applications but need mitigation against self-discharge. In the instant battery chemistry, Li|LiCl-PbCl2|Pb, reducing the diffusion coefficient of lead ions can be a way forward and a solution can be the addition of PbO to the electrolyte. The latter acts as a supplementary barrier and complements the function of the faradaic membrane. The remedial actions improved the cell’s coulombic efficiency from 92% to 97% without affecting the voltage efficiency. In addition, the limiting current density of a 500 mAh cell increased from 575 to 831 mA cm−2 and the limiting power from 2.53 to 3.66 W. Finally, the effect of PbO on the impedance and polarization of the cell was also studied.

Crystalline-silicon solar cells have dominated the photovoltaics market for the past several decades. One of the long standing challenges is the large contribution of silicon wafer cost to the overall module cost. Here, we demonstrate a simple process for making high-purity solar-grade silicon films directly from silicon dioxide via a one-step electrodeposition process in molten salt for possible photovoltaic applications. High-purity silicon films can be deposited with tunable film thickness and doping type by varying the electrodeposition conditions. These electrodeposited silicon films show about 40 to 50% of photocurrent density of a commercial silicon wafer by photoelectrochemical measurements and the highest power conversion efficiency is 3.1% as a solar cell. Compared to the conventional manufacturing process for solar grade silicon wafer production, this approach greatly reduces the capital cost and energy consumption, providing a promising strategy for low-cost silicon solar cells production., The photovoltaics market has been dominated by crystalline silicon solar cells despite the high cost of the silicon wafers. Here Zou et al. develop a one-step electrodeposition process in molten salt to produce high-purity solar-grade silicon films, delivering power conversion efficiency of 3.1%.

Abrupt Li dendrite growth and the safety hazards caused by liquid electrolytes are generally acknowledged as major technical barriers for the practical application of Li metal batteries. Solid polymer electrolytes (SPEs) are promising to overcome these obstacles, but suffer from rigidity–conductivity inconsistency, ununiform ion distribution and inferior interfacial compatibility. Herein, an anion-immobilized SPE using vinylene carbonate as the rigid polymer backbone and flexible ether oxygen chains containing anion-trapping boron moieties is proposed, which facilitates the Li+ transport and adjusts the ion distribution. This ingenious design along with facile in situ preparation effectively integrates a favorable Young's modulus (2.41 GPa), high ionic conductivity (9.11 × 10−4 S cm−1 at 25 °C) and a high Li+ transference number (0.68), as well as achieving a stable solid electrolyte interface layer. As a result, these integrative properties enable dendrite-free LiFePO4/Li batteries with excellent rate capacity (8C, 98.3 mA h g−1) and superior long-term cyclability over 600 cycles at 30 °C, providing a new strategy for safe and high-energy all-solid-state energy storage systems.

Although batteries fitted with a metal negative electrode are attractive for their higher energy density and lower complexity, the latter making them more easily recyclable, the threat of cell shorting by dendrites has stalled deployment of the technology

An in-situ formed three-layered scale consisting of a Cu-rich layer and two oxide layers on the surface of Ni10Cu11Fe alloy enables an inert anode for oxygen evolution reaction in molten Na2CO3-K2CO3. The outermost layer is mostly NiFe2O4, the middle layer mainly consists of NiO, and the innermost is a Cu-rich metal layer. The dense NiFe2O4 layer is resistant to molten salts and prevents O2− diffusing inwards, the middle NiO layer conducts electrons and functions as a buffer layer to increase the mechanical robustness of the whole scale, and the third copper-rich layer could help to slow down the oxidation rate of the alloy. This low-cost inert anode with a multi-layered scale is able to survive for more than 600 h in molten Na2CO3-K2CO3 electrolysis cell, generating O2 and thereby enabling a carbon-free electrometallurgical process.

In the realm of stationary energy storage, a plurality of candidate chemistries continues to vie for acceptance, among them the Na–NiCl2 displacement battery, which has eluded widespread adoption owing to the fragility of the β″-Al2O3 membrane. Here we report a porous electronically conductive membrane, which achieves chemical selectivity by preferred faradaic reaction instead of by regulated ionic conduction. Fitted with a porous membrane of TiN, a displacement cell comprising a liquid Pb positive electrode, a liquid Li–Pb negative electrode and a molten-salt electrolyte of PbCl2 dissolved in LiCl–KCl eutectic was cycled at a current density of 150 mA cm−2 at a temperature of 410 °C and exhibited a coulombic efficiency of 92% and a round-trip energy efficiency of 71%. As an indication of industrial scalability, we show comparable performance in a cell fitted with a faradaic membrane fashioned out of porous metal. Molten-salt batteries such as Na–NiCl2 are promising candidates for grid storage, but suffer from fragility of ion-selective ceramic membranes. Here the authors report the operation of a Li–Pb||PbCl2 battery fitted with a robust TiN mesh membrane that functions by protective faradaic reaction.

The advantages of all-solid-state batteries in terms of high energy density and improved safety have accelerated the research into durable and reliable solid electrolytes and into scale up of their processing technology. High lithium-ion-conducting Li7La3Zr2O12 (LLZO) ceramic-based solid electrolytes have been intensively studied recently, but their widespread commercial deployment has been constrained due to their fragility and brittleness. In the present study, LLZO ceramic powders have been successfully incorporated into the polyethylene oxide (PEO) polymer by tape casting. The ionic conductivity of the PEO/LLZO composite electrolyte membranes is significantly enhanced at the optimal LLZO concentration of 7.5 wt.% at which the materials exhibits maximum ionic conductivity of 5.5 × 10−4 S·cm−1 at 30 °C. The ionic conductivity enhancement mechanism of the composite electrolyte is revealed by differential scanning calorimetry (DSC), which shows that the LLZO filler represses crystallinity in PEO. Furthermore, as evidence of the advantageous electrochemical properties of the composite electrolyte an all-solid-state battery of LiFePO4/Li fabricated herein delivered a maximum discharge capacity of 150.1 mAh·g−1 at 0.1C, good cycling performance, and excellent rate capability under 60 °C.

As wind energy increases its global share of the electrical grid, the intermittency of wind becomes more problematic. To address the resulting mismatch between wind generation and grid demand, long-duration (day-long) low-cost energy storage is offered as a potential solution. Lithium-ion (Li-ion) storage is an obvious, well-developed candidate, but it is currently too expensive for such long-duration applications. Liquid metal battery (LMB) storage offers large cost reductions and recent technology developments indicate it may be viable for MW-scale storage. Accordingly, we investigate co-locating and integrating LMB and Li-ion storage within the substructure of an offshore wind turbine. Integration allows the substructure to cost-effectively double as a storage container and allows for costly electrical farm-to-shore connections to be reduced to near the average power size (by reducing peak power). These benefits are compared to the costs for battery integration. Simulations show that line size can be reduced by 20% with 4 h of storage or by 40% with 12 h of storage, with negligible capacity factor losses. However, with 24 h of average power storage using LMB, no line size reduction provided the best overall net value of the turbine-storage system due to the ability to capture all available wind energy and profit from energy arbitrage and full capacity credit. In general, LMB integrated storage results in an increased relative value with current system costs. Projected technology trends indicate that these benefits will significantly improve and that integrated Li-ion storage will also become cost-effective.

Corrosion in grid-scale energy storage devices adversely affects service lifetime and thus has a significant economic impact on their deployment. In this work, we investigate the corrosion of steel and stainless steels (SSs) as positive current collectors in the Li||Sb-Pb liquid metal battery. The erosion and formation of new phases on low-carbon steel, SS301, and SS430 were evaluated both in static conditions and under cell operating conditions. The cell performance is not adversely affected by the dissolution of iron or chromium but rather nickel. Furthermore, the in situ formation of a Fe-Cr-Sb layer helps mitigate the recession of SS430.

In the present work we show how to achieve different nanotube morphologies (namely, not only single- and double-walled tubes, but also a tube-in-tube configuration) by combining specific anodization parameters. We characterize as-grown tube layers in terms of morphology, chemical composition and properties. As-grown tubes exhibit a double-walled morphology, that is, they consist of an inner and an outer shell. The low quality inner shell can be removed by an optimized chemical treatment thus leading to nanotubes of a higher quality oxide and with a single-walled nature. Double-walled tubes grown at low electrolyte temperature provide a thick inner shell that after adequate annealing can form a unique tube-in-tube morphology.

© 2019 Elsevier Ltd The electrical potential in a battery jumps at each electrode-electrolyte interface. We present a model for computing three-dimensional current and potential distributions, which accounts for such internal voltage jumps. Within the framework of the finite volume method we discretize the Laplace and gradient operators such that they account for internal jump boundary conditions. After implementing a simple battery model in OpenFOAM we validate it using an analytical test case, and show its capabilities by simulating the current distribution and discharge curve of a Li‖Bi liquid metal battery.

The performance of a calcium-antimony (Ca-Sb) alloy serving as the positive electrode in a Ca∥Sb liquid metal battery was investigated in an electrochemical cell, Ca(in Bi) | LiCl-NaCl-CaCl[subscript 2] | Ca(in Sb). The equilibrium potential of the Ca-Sb electrode was found to lie on the interval, 1.2–0.95 V versus Ca, in good agreement with electromotive force (emf) measurements in the literature. During both alloying and dealloying of Ca at the Sb electrode, the charge transfer and mass transport at the interface are facile enough that the electrode potential varies linearly from 0.95 to 0.75 V vs Ca(s) as current density varies from 50 to 500 mA cm[superscript −2]. The discharge capacity of the Ca∥Sb cells increases as the operating temperature increases due to the higher solubility and diffusivity of Ca in Sb. The cell was successfully cycled with high coulombic efficiency (∼100%) and small fade rate (, United States. Advanced Research Projects Agency-Energy (Award DE-AR0000047), TOTAL (Firm), Marubun Research Promotion Foundation, Murata Overseas Scholarship Foundation

Calcium is an attractive electrode material for use in grid-scale electrochemical energy storage due to its low electronegativity, earth abundance, and low cost. The feasibility of combining a liquid Ca-Bi positive electrode with a molten salt electrolyte for use in liquid metal batteries at 500-700 degrees C was investigated. Exhibiting excellent reversibility up to current densities of 200 mA cm(-2), the calcium bismuth liquid alloy system is a promising positive electrode candidate for liquid metal batteries. The measurement of low self-discharge current suggests that the solubility of calcium metal in molten salt electrolytes can be sufficiently suppressed to yield high coulombic efficiencies >98%. The mechanisms giving rise to Ca-Bi electrode overpotentials were investigated in terms of associated charge transfer and mass transport resistances. The formation of low density Ca11Bi10 intermetallics at the electrode electrolyte interface limited the calcium deposition rate capability of the electrodes; however, the co-deposition of barium into bismuth from barium-containing molten salts suppressed Ca-Bi intermetallic formation thereby improving the discharge capacity. (C) 2013 Elsevier B.V. All rights reserved.

Molten oxide electrolysis (MOE) is an electrometallurgical technique that enables the direct production of metal in the liquid state from oxide feedstock, and compared with traditional methods of extractive metallurgy offers both a substantial simplification of the process and a significant reduction in energy consumption. MOE is also considered a promising route for mitigation of CO2 emissions in steelmaking, production of metals free of carbon, and generation of oxygen for extra-terrestrial exploration. Until now, MOE has been demonstrated using anode materials that are consumable (graphite for use with ferro-alloys and titanium) or unaffordable for terrestrial applications (iridium for use with iron). To enable metal production without process carbon, MOE requires an anode material that resists depletion while sustaining oxygen evolution. The challenges for iron production are threefold. First, the process temperature is in excess of 1,538 degrees Celsius (ref. 10). Second, under anodic polarization most metals inevitably corrode in such conditions. Third, iron oxide undergoes spontaneous reduction on contact with most refractory metals and even carbon. Here we show that anodes comprising chromium-based alloys exhibit limited consumption during iron extraction and oxygen evolution by MOE. The anode stability is due to the formation of an electronically conductive solid solution of chromium(iii) and aluminium oxides in the corundum structure. These findings make practicable larger-scale evaluation of MOE for the production of steel, and potentially provide a key material component enabling mitigation of greenhouse-gas emissions while producing metal of superior metallurgical quality.

Metals cannot be extracted by electrolysis of transition-metal sulfides because as liquids they are semiconductors, which exhibit high levels of electronic conduction and metal dissolution. Herein by introduction of a distinct secondary electrolyte, we reveal a high-throughput electro-desulfurization process that directly converts semiconducting molten stibnite (Sb[subscript 2]S[subscript 3]) into pure (99.9%) liquid antimony and sulfur vapour. At the bottom of the cell liquid antimony pools beneath cathodically polarized molten stibnite. At the top of the cell sulfur issues from a carbon anode immersed in an immiscible secondary molten salt electrolyte disposed above molten stibnite, thereby blocking electronic shorting across the cell. As opposed to conventional extraction practices, direct sulfide electrolysis completely avoids generation of problematic fugitive emissions (CO[subscript 2], CO and SO[subscript 2]), significantly reduces energy consumption, increases productivity in a single-step process (lower capital and operating costs) and is broadly applicable to a host of electronically conductive transition-metal chalcogenides., United States. Advanced Research Projects Agency-Energy (Award DE-AR0000047), TOTAL (Firm)

Calcium is an attractive material for the negative electrode in a rechargeable battery due to its low electronegativity (high cell voltage), double valence, earth abundance and low cost; however, the use of calcium has historically eluded researchers due to its high melting temperature, high reactivity and unfavorably high solubility in molten salts. Here we demonstrate a long-cycle-life calcium-metal-based rechargeable battery for grid-scale energy storage. By deploying a multi-cation binary electrolyte in concert with an alloyed negative electrode, calcium solubility in the electrolyte is suppressed and operating temperature is reduced. These chemical mitigation strategies also engage another element in energy storage reactions resulting in a multi-element battery. These initial results demonstrate how the synergistic effects of deploying multiple chemical mitigation strategies coupled with the relaxation of the requirement of a single itinerant ion can unlock calcium-based chemistries and produce a battery with enhanced performance., United States. Advanced Research Projects Agency-Energy, TOTAL (Firm)

The thermodynamic properties of Ca–Sb alloys were determined by emf measurements in a cell configured as Ca(s)|CaF2|Ca–Sb over the temperature range 550–830 °C. Activity coefficients of Ca and Sb, enthalpy, Gibbs free energy, and entropy of mixing of Ca–Sb alloys were calculated for xCa

The thermodynamic properties of Ca–Bi alloys were determined by electromotive force (emf) measurements to assess the suitability of Ca–Bi electrodes for electrochemical energy storage applications. Emf was measured at ambient pressure as a function of temperature between 723 K and 1173 K using a Ca(s)|CaF 2 (s)|Ca(in Bi) cell for twenty different Ca–Bi alloys spanning the entire range of composition from x Ca = 0 to 1. Reported are the temperature-independent partial molar entropy and enthalpy of calcium for each Ca–Bi alloy. Also given are the measured activities of calcium, the excess partial molar Gibbs energy of bismuth estimated from the Gibbs–Duhem equation, and the integral change in Gibbs energy for each Ca–Bi alloy at 873 K, 973 K, and 1073 K. Calcium activities at 973 K were found to be nearly constant at a value of a Ca = 1 × 10 −8 over the composition range x Ca = 0.32–0.56, yielding an emf of ∼0.77 V. Above x Ca = 0.62 and coincident with Ca 5 Bi 3 formation, the calcium activity approached unity. The Ca–Bi system was also characterized by differential scanning calorimetry over the entire range of composition. Based upon these data along with the emf measurements, a revised Ca–Bi binary phase diagram is proposed.

The electrochemical behavior of ZnTe and CdTe compound semiconductors dissolved in molten ZnCl(2) and equimolar CdCl(2)-KCl, respectively, was examined. In these melts dissolved Te is present as the divalent telluride anion, Te(2-), which was found able to be converted to elemental metal by electrochemical oxidation at the anode. ZnTe-ZnCl(2) melts were studied at 500 °C by standard electrochemical techniques. On the basis of these results, electrolysis was performed, resulting in the simultaneous extraction of phase-pure liquid Zn at the cathode and phase-pure liquid Te at the anode. This new process, involving the simultaneous deposition of liquid metals at electrodes of opposite polarity, is termed herein as ambipolar electrolysis. A melt consisting of CdTe dissolved in equimolar CdCl(2)-KCl was processed by ambipolar electrolysis, resulting in the production of liquid Cd at the cathode and liquid Te at the anode. Ambipolar electrolysis could enable new approaches to recycling compound semiconductors and semiconductor devices, such as CdTe solar cells.

The goal of this experimental study was to accurately determine the potential of the copper sulfate electrode (CSE) for use in quantitative electrochemical analysis. The potential of the CSE at 25 °C was found to be 317 mV versus that of the normal hydrogen electrode (NHE), with a slope of 0.17 mV/°C over the range from 5 °C to 45 °C. The determination of the true equilibrium potential of the CSE versus the NHE from laboratory measurements included the estimation of the liquid junction potential (LJP) by means of an electrolyte property model. The value of the LJP was estimated to be −14 mV based on calculated CSE potentials. Direct calculation of the LJP, which should have produced a more accurate result than estimation, failed to do so because the standard assumption of linear concentration variation of all species across the liquid junction was shown to be invalid.

The use of conventional lithium-ion batteries in high temperature applications (>50 ◦C) is currently inhibited by the high reactivity and volatility of liquid electrolytes. Solvent-free, solid-state polymer electrolytes allow for safe and stable operation of lithium-ion batteries, even at elevated temperatures. Recent advances in polymer synthesis have led to the development of novel materials that exhibit solidlike mechanical behavior while providing the ionic conductivities approaching that of liquid electrolytes. Here we report the successful charge and discharge cycling of a graft copolymer electrolyte (GCE)-based lithium-ion battery at temperatures up to 120 ◦ C. The GCE consists of poly(oxyethylene) methacrylate-gpoly(dimethyl siloxane) (POEM-g-PDMS) doped with lithium triflate. Using electrochemical impedance spectroscopy (EIS), we analyze the temperature stability and cycling behavior of GCE-based lithium-ion batteries comprised of a LiFePO4 cathode, a metallic lithium anode, and an electrolyte consisting of a 20-m-thick layer of lithium triflate-doped POEM-g-PDMS. Our results demonstrate the great potential of GCE-based Li-ion batteries for high-temperature applications.

Oriented silver oxide nanostructures, including polycrystalline columnar structures, nanofibers and single crystalline nanodisks, were successfully grown on conductive substrates from acetate-containing aqueous solutions through an electrochemical strategy. The morphological features (shape, diameter and areal density) of the AgxO nanostructures could be effectively adjusted through deposition parameters, including current density, concentration of silver nitrate and solution pH values. Structural and chemical analyses, based on HRTEM/SAED and XPS techniques, confirm that the electrodeposited AgxO nanostructures have a defective cubic Ag2O structure containing cation deficiency, twin boundaries, and amorphous zones and stacking faults. The variety of nanostructures obtained in this work can be attributed to the kinetic effect of supersaturation ratio of AgxO at the electrode/electrolyte interface. This electrochemical process is versatile to extend to other transition metal oxides and to a variety of inexpensive conductive substrates.

Molten oxide electrolysis (MOE) is a carbon-neutral, electrochemical technique to decompose metal oxide directly into liquid metal and oxygen gas upon use of an inert anode. What sets MOE apart from other technologies is its potential environmental advantage of no greenhouse gas emissions. Therefore, the primary challenge for carbon-free molten oxide electrolysis is the development of an inert anode. In the quest for an inert anode that can sustain the aggressive conditions of the process, iridium has been evaluated in two different slags for ironmaking. The basicity of the electrolyte proves to have a dramatic effect on the stability of the iridium anode, where iridium corrosion in an acidic slag with high silica content is less pronounced than the corrosion rate in a basic slag with high calcia content.

When considering the construction of a lunar base, the high cost ($ 100,000 a kilogram) of transporting materials to the surface of the moon is a significant barrier. Therefore in-situ resource utilization will be a key component of any lunar mission. Oxygen gas is a key resource, abundant on earth and absent on the moon. If oxygen could be produced on the moon, this provides a dual benefit. Not only does it no longer need to be transported to the surface for breathing purposes; it can also be used as a fuel oxidizer to support transportation of crew and other materials more cheaply between the surface of the moon, and lower earth orbit (approximately $20,000/kg). To this end a stable, robust (lightly manned) system is required to produce oxygen from lunar resources. Herein, we investigate the feasibility of producing oxygen, which makes up almost half of the weight of the moon by direct electrolysis of the molten lunar regolith thus achieving the generation of usable oxygen gas while producing primarily iron and silicon at the cathode from the tightly bound oxides. The silicate mixture (with compositions and mechanical properties corresponding to that of lunar regolith) is melted at temperatures near 1600 C. With an inert anode and suitable cathode, direct electrolysis (no supporting electrolyte) of the molten silicate is carried out, resulting in production of molten metallic products at the cathode and oxygen gas at the anode. The effect of anode material, sweep rate, and electrolyte composition on the electrochemical behavior was investigated and implications for scale-up are considered. The activity and stability of the candidate anode materials as well as the effect of the electrolyte composition were determined. Additionally, ex-situ capture and analysis of the anode gas to calculate the current efficiency under different voltages, currents and melt chemistries was carried out.

Production of silicon film directly by electrodeposition from molten salt would have utility in the manufacturing of photovoltaic and optoelectronic devices owing to the simplicity of the process and the attendant low capital and operating costs. Here, dense and uniform polycrystalline silicon films (thickness up to 60 µm) are electrodeposited on graphite sheet substrates at 650 °C from molten KCl–KF-1 mol% K2SiF6 salt containing 0.020–0.035 wt% tin. The growth of such high-quality tin-doped silicon films is attributable to the mediation effect of tin in the molten salt electrolyte. A four-step mechanism is proposed for the generation of the films: nucleation, island formation, island aggregation, and film formation. The electrodeposited tin-doped silicon film exhibits n-type semiconductor behavior. In liquid junction photoelectrochemical measurement, this material generates a photocurrent about 38–44% that of a commercial n-type Si wafer.

Using the layer-by-layer (LbL) assembly technique, we create a polymer-clay structure from a unique combination of LbL materials: poly(ethylene imine), Laponite clay, and poly(ethylene oxide). This trilayer LbL structure is assembled using a combination of hydrogen bonding and electrostatic interactions. The films were characterized using ellipsometry, profilometry, X-ray photon spectroscopy, atomic force microscopy, scanning electron microscopy, wide-angle X-ray diffraction, grazing-incidence small-angle X-ray scattering, and electrochemical impedance spectroscopy (EIS). We observe a layered, anisotropic structure, which resulted in in-plane ion transport 100 times faster than cross-plane at 0% relative humidity. This study represents a first application of EIS in determining anisotropic ion transport in LbL assemblies and its correlation to structural anisotropy.

The liquid metal battery (LMB) is attractive due to its simple construction, its circumvention of solid-state failure mechanisms and resultantly long lifetimes, and its particularly low levelized cost of energy. Here, we provide a study of a unique binary electrolyte, NaOH-NaI, in order to pursue a low-cost and low-temperature sodium-based liquid metal battery (LMB) for grid-scale electricity storage. Thermodynamic studies have confirmed a low eutectic melting temperature (220°C) as well as provided data to complete the phase diagram of this system. X-ray diffraction has further supported the existence of a recently discovered compound, Na[subscript 7](OH)[subscript 5]I[subscript 2], as well as offered initial evidence toward a NaI-rich compound displaying Pm-3m symmetry. These phase equilibrium data have then been used to optimize parameters from a two-sublattice thermodynamic solution model to provide a starting point for study of higher order systems. Further, a detailed electrochemical study has identified the voltage window and related oxidation/reduction reactions and found greatly improved stability of the pure sodium electrode against the electrolyte. Finally, an Na|NaOH-NaI|Pb-Bi proof-of-concept cell was assembled. This cell achieved over 100 cycles and displayed leakage currents below 0.40 mA/cm[superscript 2]. These results highlight an exciting class of low-melting molten salt electrolytes that may enable low cost grid-scale storage., United States. Advanced Research Projects Agency-Energy (Award DE-AR0000047), TOTAL (Firm), MIT Tata Center for Technology and Design

Films consisting of a vanadium pentoxide (i.e., V2O5) phase formed within a rubbery block copolymer were developed for their potential use as nanocomposite cathodes in lithium rechargeable batteries. Nanocomposite films were prepared by sol−gel synthesis from vanadyl triisopropoxide precursor in poly(oligooxyethylene methacrylate)-block-poly(butyl methacrylate), POEM-b-PBMA. The in situ growth of amorphous V2O5 was confirmed by wide-angle X-ray scattering (WAXS), X-ray photoelectron spectroscopy (XPS), and small-angle X-ray scattering (SAXS). Scanning transmission electron microscopy (STEM) and differential scanning calorimetry (DSC) demonstrated the selective incorporation of vanadium oxide within the ion-conducting POEM domains, while the oxide morphology was revealed by TEM to be a filamentous network. Cyclic voltammetry and impedance spectroscopy confirmed the preservation of the redox properties of the vanadium oxide and the ion-conductive properties of the polymer in hybrid films. Co-assembled nanoc...

Solid-state polymer–silicate nanocomposite electrolytes based on an amorphous polymer poly[(oxyethylene) 8 methacrylate], POEM, and lithium montmorillonite clay were fabricated and characterized to investigate the feasibility of their use as ‘salt-free’ electrolytes in lithium polymer batteries. X-ray scattering and transmission electron microscopy studies indicate the formation of an intercalated morphology in the nanocomposites due to favorable interactions between the polymer matrix and the clay. The morphology of the nanocomposite is intricately linked to the amount of silicate in the system. At low clay contents, dynamic rheological testing verifies that silicate incorporation enhances the mechanical properties of POEM, while impedance spectroscopy shows an improvement in electrical properties. With clay content ≥15 wt.%, mechanical properties are further improved but the formation of an apparent superlattice structure correlates with a loss in the electrical properties of the nanocomposite. The use of suitably modified clays in nanocomposites with high clay contents eliminates this superstructure formation, yielding materials with enhanced performance.

Orthorhombic LiMnO2 exhibits complex magnetic behavior. In addition to short- and long-range antiferromagnetic ordering, we observed spin-glass behavior in the reported temperature regime of long-range antiferromagnetic ordering. Lithium extraction from LiMnO2 further complicates its magnetic behavior. A broad maximum of susceptibility at ≈360 K, characteristic of well-ordered LiMnO2, disappears upon electrochemical delithiation to Li0.39MnO2, indicating that two-dimensional ordering on the folded triangular Mn lattice in LiMnO2 is destroyed as the cation sublattice begins to transform to a spinel. Spin-glass behavior is, however, observed in Li0.39MnO2 as well. Compared to conventionally prepared spinel LiMn2O4, a lower degree of frustration is deduced, which is attributed to incomplete spinel ordering in the early stages of the cycling-induced transformation. In addition, the fraction of Mn ions occupying tetrahedral sites during the spinel transformation has been quantitatively determined for the first time, using magnetic susceptibility data. The results, surprisingly, support the existence of low-spin Mn ions on tetrahedral sites in the electrochemically transformed spinel.

Batteries are an attractive option for grid-scale energy storage applications because of their small footprint and flexible siting. A high-temperature (700 °C) magnesium-antimony (Mg||Sb) liquid metal battery comprising a negative electrode of Mg, a molten salt electrolyte (MgCl(2)-KCl-NaCl), and a positive electrode of Sb is proposed and characterized. Because of the immiscibility of the contiguous salt and metal phases, they stratify by density into three distinct layers. Cells were cycled at rates ranging from 50 to 200 mA/cm(2) and demonstrated up to 69% DC-DC energy efficiency. The self-segregating nature of the battery components and the use of low-cost materials results in a promising technology for stationary energy storage applications.

The full potential of wireless devices remains unattainable due to limitations in battery performance. It is the thesis of the guest editors and contributing authors of this issue of MRS Bulletin that there is much room for improvement, that we are still far from the practical limits of the technology, and that materials research has the capability to pave the way for a new generation of rechargeable batteries that will offer a dramatic improvement in power delivery over anything available today. The basics of battery operation, including the relevant electrochemistry, are reviewed, unsolved problems are enumerated, and prospective solutions are indicated.

The electrochemical behavior of a ternary eutectic mixture of sodium amide (NaNH2), sodium hydroxide (NaOH) and sodium iodide (NaI) was investigated to elucidate its validity as an electrolyte for sodium-based liquid metal batteries. The liquid metal battery consists of two metals with different electronegativity separated by molten salt. The self-segregating nature of the three layers allows for easy assembly and scalability. Moreover, the all-liquid design allows the batteries to operate at high current densities with negligible losses because of the high conductivity of molten salts and fast transport properties in the liquid state. Sodium-based liquid metal batteries are particularly attractive due to the low cost of sodium metal (Na) and its low melting temperature (98°C). However, due to the high melting temperature of sodium halide salt (Tm > 500°C), the early efforts to build a sodium-based liquid metal battery faced the obstacle of high self-discharge and short life cycle.1 In our previous work, using a eutectic NaOH-NaI salt (Tm: 223°C), we demonstrated a Na||Bi-Pb cell operated at lower temperature ~250°C with small self-discharge. In order to further decrease operating temperature to less than 200 °C, in this work, we investigated a ternary eutectic 52%NaNH2,38%NaOH and 10%NaI (Tm: 127°C) 2. By using a three-electrode setup consisting of a liquid Na in β"-Al2O3 as a reference electrode, and tungsten wires as counter and working electrodes, cyclic voltammetry was performed at different scan rates (50, 100, and 200 mVs-1) and at 180 °C operating temperature. The electrochemical window of the ternary electrolyte was identified as 1.3 V with the sodium deposition as the cathodic limit and the oxidation of NH2 - anions to form N2H4gas as the anodic limit. Bismuth-lead (Bi-Pb) alloy is a candidate for positive electrode due to its low eutectic point (125 °C). Known thermodynamic properties of Na-Bi-Pb3 and previous work4 indicate that the operating voltage of the Na||Bi-Pb cell is expected to be within the electrochemical window of NaNH2-NaOH-NaI electrolyte. In this work, we focused on the discharge behavior of positive electrode, corresponding to the alloying process of Na in Bi-Pb alloy, in the ternary electrolyte. Using a similar three electrode setup utilizing liquid Na in β"-Al2O3 reference electrode, eutectic Bi-Pb working electrodes and a Na-Bi-Pb counter electrode, we obtained the voltage-time trace during alloying process and prepared the samples at varying Na concentration and current densities at 180°C operating temperature. The samples were quenched at target concentration of Na and cross-sectioned samples were analyzed using energy dispersive x-ray spectroscopy and scanning electron microscopy. We found that the Na preferentially alloys with Bi due to its stronger interaction than that with Pb (Pb works as diluent) and forms intermetallic, such as Na3Bi, similar to Li-Sb-Pb system 5 and Ca-Sb-Pb system.6 A smooth voltage profile on discharging to 10 at% of Na in the Bi-Pb electrode at 100 mAcm-2suggests potential feasibility of the ternary electrolyte for the sodium-based liquid metal batteries. References [1] A. D. Cairns, E.J. , Crouthamel, C.E. , Fischer, A.K. , Foster, M.S. , Hesson, J.C. , Johnson, C.E. , Shimotake, H. , Tevebaugh, “Galvanic cells with fused electrolytes,”, ANL-7316, Argonne National Laboratory, Chicago, 1967. [2] L. Heredy, “Fusible alkali-metal salt electrolyte,” US 3,472,745, 1969. [3] A. Petric, A. D. Pelton, M. L. Saboungi, W. F. Calaway, P. J. Tumidajski, A. Petric, J. C. Thompson, R. N. Singh, F. Sommer, B. P. Alblas, W. Van Der Lugt, M. Revere, M. P. Tosi, S. Tamaki, T. Ishiguro, and S. Takeda, “Dilute solutions of sodium in molten bismuth and tin : EMF measurements and interpretation,” J. Phys. F Met. Phys., 1983. [4] B. L. Spatocco, T. Ouchi, G. Lambotte, P. J. Burke, and D. R. Sadoway, “Low-Temperature Molten Salt Electrolytes for Membrane-Free Sodium Metal Batteries,” J. Electrochem. Soc., vol. 162, no. 14, pp. A2729–A2736, 2015. [5] K. Wang, K. Jiang, B. Chung, T. Ouchi, P. J. Burke, D. a. Boysen, D. J. Bradwell, H. Kim, U. Muecke, and D. R. Sadoway, “Lithium–antimony–lead liquid metal battery for grid-level energy storage,” Nature, vol. 514, no. 7522, pp. 348–350, 2014. [6] S. Poizeau and D. R. Sadoway, “Application of the Molecular Interaction Volume Model (MIVM) to Calcium-Based Liquid Alloys of Systems Forming High-Melting Intermetallics,” J. Am. Chem. Soc., vol. 135, no. 22, pp. 8260–8265, Jun. 2013.