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Results for “Molten Electrolytes”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Stable electrolyte matrix for molten carbonate fuel cells

An electrolyte matrix for use with molten carbonate fuel cells having an enhanced stability and lifetime is provided. The electrolyte matrix includes lithium aluminate as a support material and a coarsening inhibitor. The coarsening inhibitor may be in the form of discrete particles or a dopant present in the support material. The coarsening inhibitor may include MnO 2 , Mn 2 O 3 , TiO 2 , ZrO 2 , Fe 2 O 3 , LiFe 2 O 3 , or mixtures thereof. The coarsening inhibitor prevents the formation of large pores in the electrolyte matrix during operation of the fuel cell, increasing the performance and the service lifetime of the electrolyte matrix.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2022

Binder for electrolyte matrix for molten carbonate fuel cells

A binder solution for an electrolyte matrix for use with molten carbonate fuel cells is provided. The binder solution includes a first polymer with a molecular weight of less than about 150,000 and a second binder with a molecular weight of greater than about 200,000. The binder solution produces an electrolyte matrix with improved flexibility, matrix particle packing density, strength, and pore structure.

Surendranath, Arun↗
DOE OSTI2026

Precious metal oxygen-evolving anodes for electrolytic reduction of metal oxides in molten LiCl-Li 2 O electrolyte

Understanding the electrochemical stability of oxygen-evolving anode materials in molten salt electrolytes is essential to enable decarbonized electrolytic reduction of metal oxides (e.g., used nuclear oxide fuels). Here, this work investigated three precious metals (Ir, Ru, and Pt) as oxygen-evolving anodes in molten LiCl-Li 2 O (99.0-1.0 wt%) at 650 °C. For consistent measurements, this work employed a three-electrode cell comprised of a two-phase Li-Bi (65-35 at%) reference electrode and a NiO counter electrode. Anodic polarization behavior of each anode was investigated via cyclic voltammetry (CV) and chronoamperometry. The onset potential for oxygen evolution was observed at E > 2.9 V (vs. Li/Li + ) for the Ir and Ru anodes and anodic current density was as high as 1.0 A cm -2 at 3.23 V. The dimensional stability of each anode was evaluated from long-term electrolysis experiments (10.0-32.1 h) at 3.23 V. Rapid consumption of the Pt anode was observed after the application of 26,453 C cm -2 with a reduction in diameter of about 15.8% due to the formation of a non-protective Li 2 PtO 3 compound. The formation of this compound was also observed during CV measurements as additional anodic waves at potentials more negative than that of oxygen evolution. In contrast, both the Ir and Ru anodes exhibited excellent dimensional stability with a reduction in diameter or thickness of less than 1.5% even after applying greater charge density of ~41,100 C cm -2 , demonstrating superior stability during oxygen evolution in the LiCl-Li 2 O electrolyte.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Stable electrolyte matrix for molten carbonate fuel cells

A method of making an electrolyte matrix includes: preparing a slurry comprising a support material, a coarsening inhibitor, an electrolyte material, and a solvent; and drying the slurry to form an electrolyte matrix. The support material comprises lithium aluminate, the coarsening inhibitor comprises a material selected from the group consisting of MnO 2 , Mn 2 O 3 , TiO 2 , ZrO 2 , Fe 2 O 3 , LiFe 2 O 3 , and mixtures thereof, and the coarsening inhibitor has a particle size of about 0.005 μm to about 0.5 μm.

Hilmi, Abdelkader↗
DOE OSTI2020

Sodium-halogen secondary cell

An intermediate temperature sodium-halogen secondary cell that includes a negative electrode compartment housing a negative, molten sodium-based electrode and a positive electrode compartment housing a current collector disposed in a highly conductive molten positive electrolyte. A sodium halide (NaX) positive electrode is disposed in a molten positive electrolyte comprising one or more AlX3 salts, wherein X may be the same or different halogen selected from Cl, Br, and I, wherein the ratio of NaX to AlX3 is greater than or equal to one. A sodium ion conductive solid electrolyte membrane separates the molten sodium negative electrode from the molten positive electrolyte. The secondary cell operates at a temperature in the range from about 80° C. to 210° C.

Bhavaraju, Sai↗
NASA NTRS1994

Fundamental Aspects of Ion Transport in Solid Electrolytes

Solid electrolytes (also termed as superionic solids or fast ion conductors) are characterized by high electrical conductivity, comparable to concentrated liquid electrolytes or even molten salt electrolytes, made possible by rapid transport of ions in the crystalline lattice.

electrochemistry solid state ionics superionic sol↗
DOE OSTI2021

Electrolytic Reduction of Titanium Dioxide in Molten LiCl–Li2O

The electrolytic reduction of TiO2 in LiCl–Li2O (1 wt.%) at 650 °C was investigated under a series of cathodic reduction potentials and applied charges to provide a mechanistic understanding of the electrochemical characteristics of the system. The optimal cathodic reduction potential was determined as being −0.3 V vs. Li/Li+. Li2TiO3 and LiTiO2 were structurally identified as intermediate and partial reduction products of the TiO2 electrolytic reduction. The reduction of LiTiO2 was extremely slow and reversible due to its high stability and the detrimental effect of Li2O accumulation within the solid particles. The most reduced product obtained in this study was LiTiO2, which was achieved when using 150% of the theoretical charge under the optimal reduction potential. The highest reduction extent obtained in this study was 25%. Based on theoretical DFT modeling, a detailed multistep reduction mechanism and scheme were proposed for TiO2 electrolytic reduction in LiCl–Li2O (1 wt.%) at 650 °C.

Shi, Meng↗
DOE OSTI2020

A High-Performance Na-Al Battery Based on Reversible NaAlCl4 Catholyte

This work demonstrates a high-capacity and safe Na-Al battery pairing sodium metal anode and reversible NaAlCl4 catholyte for grid scale energy storage applications. The energy-rich sodium anode allows the full play of the aluminum cathode, resulting in a full-cell capacity of 308 mAh/g at a discharge voltage of 1.6 V. Benefiting from the use of ??-alumina solid electrolyte (BASE), molten sodium anode and reversible Al deposition/stripping from NaAlCl4 catholyte, the battery presents a stable Coulombic efficiency of 100% and energy efficiency of ~95%. At a rate of C/3 (6.77 mA/cm2), the cell maintains 282 mAh/g (447 Wh/kg) after 200 cycles with an excellent capacity retention of 97.6%. Moreover, we elucidate pathways to build sodium-anode-free cells from the discharged state under dry air, which further extends the feasibility of this battery for stationary storage applications. These findings are expected to provide a new platform for the development of practical Al batteries.

Zhan, Xiaowen↗
NASA NTRS1990

Symposium on Rechargeable Lithium Batteries, Hollywood, FL, Oct. 19-24, 1989, Proceedings

Recent advances in the technology and applications of rechargeable Li cells are discussed in reviews and reports. A general overview of the field is provided, and sections are devoted to organic electrolyte systems, polymeric electrolyte systems, inorganic electrolytes systems, and molten-salt electrolytes. Particular attention is given to electrolyte stabilization, the effects of organic additives on electrolyte performance, a cycle-life sensor, consumer-product applications, in situ measurements of gas evolution in Li secondary cells, ultrathin polymer cathodes, electrochemical growth of conducting polymers, and sealing Li/FeS(x) cells for a bipolar battery.

Subbarao, S.↗
DOE OSTI2026

Development of a Chlorine Cathode and Anode Basket Assembly for Production of Uranium Chloride

A chlorine cathode has been developed for in situ chlorination of metals, oxides, and oxychlorides in molten chloride electrolytes that could be used to support synthesis of chloride fuel salts for molten salt reactors. The chlorine cathode is designed to electrochemically reduce chlorine gas to generate chloride ions that, when paired with a metal anode, chlorinate that metal as it is oxidized into the salt. The designed porous carbon electrode effectively distributes Cl 2 to the electrode surface and efficiently generates Clions in the molten chloride electrolyte. This report highlights recent improvements made to the electrode assembly, with a focus on operational control of the anode basket stability. Synthesis tests demonstrated the successful chlorination of uranium metal, resulting in 3.6 wt% uranium generated in the LiCl-KCl base salt in 45 minutes, performed in a bench-scale chlorination apparatus. Higher concentrations could be achieved by applying longer chlorination times or increasing the amount of uranium loaded in the anode basket. Overall, the chlorine cathode can be used with an appropriately designed anode to chlorinate uranium in situ for synthesis of molten salt reactor fuel salts.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1982

Studies of metals electroprocessing in molten salts

Fluid flow patterns in molten salt electrolytes were observed in order to determine how mass transport affects the morphology of the metal deposit. Studies conducted on the same metal, both in aqueous electrolytes in which coherent solid electrodeposits are produced, as well as in transparent molten salt electrolytes are described. Process variables such as current density and composition of the electrolyte are adjusted to change the morphology of the electrodeposit and, thus, to permit the study of the nature of electrolyte flow in relation to the quality of the electrodeposit.

Sadoway, D. R.↗
DOE OSTI2023

Management of Alkali and Alkaline Earth Fission Products in Used Pyroprocessing Salt

Pyroprocessing of spent nuclear fuel (SNF) involves dissolving metallic fuel into a molten salt electrolyte (typically eutectic LiCl-KCl) and then preferentially depositing actinides onto inert cathodes. Subsequent operations include drawdown of residual actinides and lanthanides from the electrolyte prior to re-using the salt. The recovered actinides are recycled and the recovered lanthanides are disposed as waste. Alkali and alkaline earth metal fission products in the fuel, such as Cs, Sr and Ba, dissolve into the salt during electrorefining. The concentrations of these elements buildup over time in the molten salt electrolyte, which may change the freezing point. The radioactive decay of 137 Cs and 90 Sr (half life 30 and 29 years) generates significant heat and produces strong ionizing radiation fields (β and γ). The increasing heat load and radioactivity as these elements build up in the molten salt requires frequent replacement and disposal of the electrolyte salt. Alternatively, the salt can be treated to remove these and other elements and then recycled to the electrorefiner. An effective strategy to manage these alkali and alkaline earth metal fission products in the molten salt electrolyte would increase the efficiency of pyroprocessing and decrease the volume of salt waste requiring disposal. Alkali and alkaline earth metal fission products are extremely stable in molten salt as chlorides--even more stable than the LiCl-KCl eutectic base salt--making them challenging to remove. They are not removed during drawdown operations to recover residual actinides and lanthanides and a separate operation is required to sufficiently purify the salt for reuse. This work is focused on selecting a method for separating Cs, Sr and Ba from the salt recovered from the lanthanide drawdown operation prior to recycling the cleaned salt back to the electrorefiner. Not addressed in this work is the management of the waste stream produced by the separation. This report summarizes the issues to be addressed when developing removal strategies for cesium, strontium, and barium and reviews existing methods to identify suitable methods and any technological gaps in their application.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2010

Performance Testing of Molten Regolith Electrolysis with Transfer of Molten Material for the Production of Oxygen and Metals on the Moon

Previously, we have demonstrated the production of oxygen by electrolysis of molten regolith simulants at temperatures near 1600 C. Using an inert anode and suitable cathode, direct electrolysis (no supporting electrolyte) of the molten silicate is carried out, resulting in the production of molten metallic products at the cathode and oxygen gas at the anode. Initial direct measurements of current efficiency have confirmed that the process offer potential advantages of high oxygen production rates in a smaller footprint facility landed on the moon, with a minimum of consumables brought from Earth. We now report the results of a scale-up effort toward the goal of achieving production rates equivalent to 1 metric ton O2/year, a benchmark established for the support of a lunar base. We previously reported on the electrochemical behavior of the molten electrolyte as dependent on anode material, sweep rate and electrolyte composition in batches of 20-200g and at currents of less than 0.5 A. In this paper, we present the results of experiments performed at currents up to 10 Amperes) and in larger volumes of regolith simulant (500 g - 1 kg) for longer durations of electrolysis. The technical development of critical design components is described, including: inert anodes capable of passing continuous currents of several Amperes, container materials selection, direct gas analysis capability to determine the gas components co-evolving with oxygen. To allow a continuous process, a system has been designed and tested to enable the withdrawal of cathodically-reduced molten metals and spent molten oxide electrolyte. The performance of the withdrawal system is presented and critiqued. The design of the electrolytic cell and the configuration of the furnace were supported by modeling the thermal environment of the system in an effort to realize a balance between external heating and internal joule heating. We will discuss the impact these simulations and experimental findings have on the design of a suitable prototype for lunar applications

Sibille, Laurent↗
NASA NTRS1982

Electro Processing Research

Electroprocessing which is concerned with fluid dynamics of the electroreduction process to determine how it may be modified to improve the quality of the deposit was studied. Experimental techniques are used in this research. These techniques include laser Schlieren photography, laser Doppler velocimetry, and frequency spectrum analysis. Projects involve fluid flow studies of zinc plating in aqueous and molten salt electrolytes, study of cell design for magnesium chlorides electrolysis, digital signal analysis of manganese electrodeposition in molten chlorides, and electroplating of molybdenum from low melting salts. It is anticipated that the use of refractory metals as constructed materials in engineering will increase. Their electrodeposition from molten salt electrolytes is important in the extraction metallurgy of refractory metals.

Source record↗
DOE OSTI2023

Electrode Blocking Due to Redox Reactions in Aluminum Chloride-Sodium Iodide Molten Salts

Iodide redox reactions in molten NaI/AlCl 3 are shown to generate surface-blocking films, which may limit the useful cycling rates and energy densities of molten sodium batteries below 150 °C. An experimental investigation of electrode interfacial stability at 110 °C reveals the source of the reaction rate limitations. Electrochemical experiments in a 3-electrode configuration confirm an increase of resistance on the electrode surface after oxidation or reduction current is passed. Using chronopotentiometry, chronoamperometry, cyclic voltammetry, and electrochemical impedance spectroscopy, the film formation is shown to depend on the electrode material (W, Mo, Ta, or glassy carbon), as well as the Lewis acidity and molar ratio of I − /I 3 − in the molten salt electrolytes. These factors impact the amount of charge that can be passed at a given current density prior to developing excessive overpotential due to film formation that blocks the electrode surface. The results presented here guide the design and use of iodide-based molten salt electrolytes and electrode materials for grid scale battery applications.

25 ENERGY STORAGE↗
DOE OSTI2024

Chemical and electrochemical pathways to low-carbon iron and steel

Currently, the iron and steel industry is responsible for 7% of global CO 2 emissions. In this review, we summarize the operational principles of current emissions-intensive steelmaking technologies and review emerging low- and zero-carbon technologies that could substantially reduce emissions. Current technologies that are discussed include blast furnaces, electric arc furnaces, and smelting. Promising low-carbon routes include use of alternative reductants for ore processing (hydrogen direct reduction, hydrogen plasma-smelting, hydrogen smelting, and ammonia-based reduction), electrolytic iron production (with aqueous and molten oxide electrolytes) and biocarbon-based electric arc furnace operation. Advantages of each approach are presented, and remaining research hurdles are identified.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Multi-species electrolyte migration kinetics with directed flow

Here, this paper investigates an electrochemical process designed to control mixing kinetics in liquid electrolytes. The process utilizes an electrochemical cell with anode and cathode chambers connected by a channel without a membrane. This configuration depletes multiple electroactive species in the cathode chamber while selectively replenishing them in the anode chamber. A key application is the removal of impurity species from the cathode chamber electrolyte and the selective replenishment of primary electroactive species in the anode chamber. Aqueous cell experiments were conducted to validate the theoretical model, and simulations were performed for molten salt electrolytes. This approach minimizes waste by reducing the need for additional electrolyte supplies and extends the utilization of anion species, contributing to environmentally sustainable electrochemical materials processing.

Electrochemical Process↗