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Molten Salt Reactors is a comprehensive reference on the status of molten salt reactor (MSR) research and thorium fuel utilization.There is growing awareness that nuclear energy is needed to complement intermittent energy sources and to avoid pollution from fossil fuels.

Solid-state sodium (Na) batteries have received extensive attention as a promising alternative to room-temperature liquid electrolyte Na-ion batteries and high-temperature liquid electrode Na–S batteries because of safety concerns. However, the major issues for solid-state Na batteries are a high interfacial resistance between solid electrolytes and electrodes, and Na dendrite growth. Here we report that a yttria-stabilized zirconia (YSZ)-enhanced beta-alumina solid electrolyte (YSZ@BASE) has an extremely low interface impedance of 3.6 Ω cm 2 with the Na metal anode at 80 °C, and also exhibits an extremely high critical current density of ~7.0 mA cm –2 compared with those of other Li- and Na-ion solid electrolytes reported so far. With a trace amount of eutectic NaFSI–KFSI molten salt at the electrolyte/cathode interface, a quasi-solid-state Na/YSZ@BASE/NaNi 0.45 Cu 0.05 Mn 0.4 Ti 0.1 O 2 full cell achieves a high capacity of 110 mAh g –1 with a Coulombic efficiency >99.99% and retains 73% of the cell capacity over 500 cycles at 4C and 80 °C. Extensive characterizations and theoretical calculations prove that the stable β-NaAlO 2 -rich solid–electrolyte interphase and strong YSZ support matrix play a critical role in suppressing the Na dendrite as they maintain robust interfacial contacts, lower electronic conduction and prevent the continual reduction of BASE through oxygen-ion compensation. Beta-alumina solid electrolyte enhanced by yttria-stabilized zirconia can provide a very low interfacial impedance with a sodium metal anode and a critical current density higher than those previously reported in lithium and sodium batteries.

Molten salt aluminum-sulfur batteries are based exclusively on resourcefully sustainable materials, and are promising for large-scale energy storage owed to their high-rate capability and moderate energy density; but the operating temperature is still high, prohibiting their applications. Here we report a rapid-charging aluminium-sulfur battery operated at a sub-water-boiling temperature of 85 °C with a tamed quaternary molten salt electrolyte. The quaternary alkali chloroaluminate melt – possessing abundant electrochemically active high-order Al-Cl clusters and yet exhibiting a low melting point – facilitates fast Al 3+ desolvation. A nitrogen-functionalized porous carbon further mediates the sulfur reaction, enabling the battery with rapid-charging capability and excellent cycling stability with 85.4% capacity retention over 1400 cycles at a charging rate of 1 C. Importantly, we demonstrate that the asymmetric sulfur reaction mechanism that involves formation of polysulfide intermediates, as revealed by operando X-ray absorption spectroscopy, accounts for the high reaction kinetics at such temperature wherein the thermal management can be greatly simplified by using water as the heating media. Molten salt aluminium-sulfur batteries exhibit high-rate capability and moderate energy density, but suffer from high operating temperature. Here the authors demonstrate a rapidly charging aluminum-sulfur battery operating at 85 °C enabled by a quaternary alkali chloroaluminate electrolyte.

Owing to the low atomic weight of fluorine, rechargeable fluoride-based batteries could offer very high energy density. However, current batteries need to operate at high temperatures that are required for the molten salt electrolytes. Davis et al. push toward batteries that can operate at room temperature, through two advances. One is the development of a room-temperature liquid electrolyte based on a stable tetraalkylammonium salt–fluorinated ether combination. The second is a copper–lanthanum trifluoride core-shell cathode material that demonstrates reversible partial fluorination and defluorination reactions. Science , this issue p. 1144 Fluoride ion–conducting liquid electrolytes enable room-temperature cycling of fluoride ion electrochemical cells. Fluoride ion batteries are potential “next-generation” electrochemical storage devices that offer high energy density. At present, such batteries are limited to operation at high temperatures because suitable fluoride ion–conducting electrolytes are known only in the solid state. We report a liquid fluoride ion–conducting electrolyte with high ionic conductivity, wide operating voltage, and robust chemical stability based on dry tetraalkylammonium fluoride salts in ether solvents. Pairing this liquid electrolyte with a copper–lanthanum trifluoride (Cu@LaF 3 ) core-shell cathode, we demonstrate reversible fluorination and defluorination reactions in a fluoride ion electrochemical cell cycled at room temperature. Fluoride ion–mediated electrochemistry offers a pathway toward developing capacities beyond that of lithium ion technology.

Designing synergistic heterogeneous catalytic interfaces is the key to developing highly compatible pH‐universal electrocatalysts for complex chemical environments. Our theoretical calculation results demonstrate that the Ru‐Ru2P heterointerface can not only promote the redistribution of charges, but also reduce the d‐band center, and then enhances the adsorption capacity of the key intermediate. However, in situ and facile synthesis of Ru‐Ru2P heterostructures is severely limited by thermodynamic obstacles. Herein, we propose a molten salt‐assisted catalytic synthesis scheme, and successfully build a series of homologous metallic Ru‐Ru2P heterostructure catalysts with different molar ratios of Ru to P under atmospheric pressure and low‐temperature (400°C). The resultant Ru‐Ru2P with rich heterostructures show the Pt‐like HER performance in different pH media. Particularly, it is prominent under alkaline conditions (18 mV @ 10 mA cm−2), which outperforms the Pt catalyst (37 mV @ 10 mA cm−2). Furthermore, Ru‐Ru2P heterostructures also show certain potential in the electrolysis of seawater to produce hydrogen. This work represents a significant supplement of high‐efficiency pH‐universal HER catalysts, and provides a new light on interface engineering in energy technology fields and beyond. A low‐temperature solid phase route is formulated to form controllable Ru‐Ru2P heterointerfaces with homologous Ru where the higher electronic state crosses the Fermi level and then lowers the d‐band center, thereby allowing the catalyst with Pt‐like pH‐universal hydrogen evolution reaction kinetics.

Corrosion is a ubiquitous failure mode of materials. Often, the progression of localized corrosion is accompanied by the evolution of porosity in materials previously reported to be either three-dimensional or two-dimensional. However, using new tools and analysis techniques, we have realized that a more localized form of corrosion, which we call 1D wormhole corrosion, has previously been miscategorized in some situations. Using electron tomography, we show multiple examples of this 1D and percolating morphology. To understand the origin of this mechanism in a Ni-Cr alloy corroded by molten salt, we combined energy-filtered four-dimensional scanning transmission electron microscopy and ab initio density functional theory calculations to develop a vacancy mapping method with nanometer-resolution, identifying a remarkably high vacancy concentration in the diffusion-induced grain boundary migration zone, up to 100 times the equilibrium value at the melting point. Deciphering the origins of 1D corrosion is an important step towards designing structural materials with enhanced corrosion resistance. Corrosion is a ubiquitous failure mode in materials. Here the authors report a percolating 1D wormhole corrosion morphology using advanced electron microscopy and theoretical simulations. The work presents a vacancy mapping method with nm-resolution, identifying the incubation sites of the wormholes.

Molten salt is an excellent medium for chemical reaction, energy transfer, and storage. Molten salt innovative technologies should be developed to recover metals from secondary resources and reserve metals from primary natural sources. Among these technologies, molten salt electrolysis is an economic and environment-friendly method to extract metals from waste materials. From the perspective of molten salt characteristics, the application of molten salts in chemistry, electrochemistry, energy, and thermal storage should be comprehensively elaborated. This review discusses further directions for the research and development of molten salt electrolysis and their use for metal recovery from various metal wastes, such as magnet scrap, nuclear waste, and cemented carbide scrap. Attention is placed on the development of various electrolysis methods for different metal containing wastes, overcoming some problems in electrolytes, electrodes, and electrolytic cells. Special focus is given to future development directions for current associated processing obstacles.

Conventional solid-to-solid conversion-type cathodes in batteries suffer from poor diffusion/reaction kinetics, large volume changes and aggressive structural degradation, particularly for rechargeable aluminium batteries (RABs). Here we report a class of high-capacity redox couples featuring a solution-to-solid conversion chemistry with well-manipulated solubility as cathodes—uniquely allowed by using molten salt electrolytes—that enable fast-charging and long-lived RABs. As a proof-of-concept, we demonstrate a highly reversible redox couple—the highly soluble InCl and the sparingly soluble InCl 3 —that exhibits a high capacity of about 327 mAh g −1 with negligible cell overpotential of only 35 mV at 1 C rate and 150 °C. The cells show almost no capacity fade over 500 cycles at a 20 C charging rate and can sustain 100 mAh g −1 at 50 C. The fast oxidation kinetics of the solution phase upon initiating the charge enables the cell with ultrafast charging capability, whereas the structure self-healing via re-forming the solution phase at the end of discharge endows the long-term cycling stability. This solution-to-solid mechanism will unlock more multivalent battery cathodes that are attractive in cost but plagued by poor reaction kinetics and short cycle life. Conventional solid-to-solid conversion cathodes in rechargeable aluminium batteries suffer from sluggish reaction kinetics and cumulative structural degradation. Here the authors disclose a solution-to-solid conversion chemistry using molten salt electrolytes to achieve fast-charging capability and good cycling stability.

Graphite has been used in a wide range of applications since the discovery due to its great chemical stability, excellent electrical conductivity, availability, and ease of processing. However, the synthesis of graphite materials still remains energy‐intensive as they are usually produced through a high‐temperature treatment (>3000°C). Herein, we introduce a molten salt electrochemical approach utilizing carbon dioxide (CO2) or amorphous carbons as raw precursors for graphite synthesis. With the assistance of molten salts, the processes can be conducted at moderate temperatures (700–850°C). The mechanisms of the electrochemical conversion of CO2 and amorphous carbons into graphitic materials are presented. Furthermore, the factors that affect the graphitization degree of the prepared graphitic products, such as molten salt composition, working temperature, cell voltage, additives, and electrodes, are discussed. The energy storage applications of these graphitic carbons in batteries and supercapacitors are also summarized. Moreover, the energy consumption and cost estimation of the processes are reviewed, which provides perspectives on the large‐scale synthesis of graphitic carbons using this molten salt electrochemical strategy. This review shows that CO2 gas or biomass‐derived carbons could be utilized as raw precursors for the preparation of graphitic carbons via a molten salt electrochemical route. In this review, we discuss the factors that affect the graphitization, the costs of the processes, and the challenges that need to be tackled. The molten salt approach has shown great promise in large‐scale synthesis of high‐quality graphite materials in future.

Recent advancements in nuclear technology, particularly in the development of small modular reactors (SMRs) and the implementation of enhanced safety protocols, have significantly increased the attractiveness of nuclear energy as a sustainable power source. This growing demand for nuclear energy, coupled with the proliferation of SMRs, has led to a heightened demand for uranium, consequently driving up its market price. As uranium resources become increasingly scarce, there is a growing interest in technologies that recycle used nuclear fuel or reuse as fuel. Pyroprocessing is an advanced technique for recycling used nuclear fuel from light-water reactors into metallic fuel suitable for fast reactors. This process, which relies on molten salt, involves the reduction of UNF to the metal via oxide reduction using a Li2O–LiCl salt as an electrolyte. Subsequently, fuel components are recovered through electrorecovery methods, including electrorefining and electrowinning, utilizing a LiCl–KCl–UCl3 salt. This review paper examines the critical technologies involved in oxide reduction and electrorecovery processes, which are essential for commercializing of these techniques. It provides a comprehensive overview of recent research and literature, with a specific emphasis on the development of electrode materials that enhance process efficiency, the production of UCl3 for electrorecovery, and key advancements in electrowinning technology.