The electrification of transportation and the transition of society towards low or net-zero carbon emissions has led to a skyrocketing global demand for Li-ion batteries. After a service life of three to ten years, Li-ion batteries have less than 80 % of their initial capacities and draw near to the end of their lives for practical utilization. Due to potential supply chain shortages and the value embodied in Li-ion batteries, it is imperative to recycle them, to recover the materials, and to improve the circularity and the sustinability of the industry. How to cost-effectively purify spent batteries while reducing time, energy, and waste emissions is a challenge faced by Li-ion battery recyclers. The first electrochemical membrane reactor reported in our group hasa high selectivity towards lower Cu2+, Al3+ and Fe3+ ions (<5 ppm) and retains > 95 % of the Ni2+, Co2+ and Mn2+ ions in the leachate. An advanced electrochemical membrane reactor was developed in this study. Not only does the new reactor have the same selectivity as the original reactor, but other advantages including a faster leachate processing rate (up to 10X faster). The advanced reactor can also directly generate acid at the anode side; eliminating the reactor restoration step. The prominent advantages that this electrodialysis technology has over chemical-precipitation methods include: (1) ion recovery efficiencies do not diminish after removing the impurities, Ni2+, Co2+ and Mn2+, even at a higher initial Ni2+ ion concentrations; in comparison, chemical precipitation has Ni2+, Co2+ and Mn2+ ion recovery efficiencies reduced significantly when the initial Ni2+, Co2+ and Mn2+ ion concentrations increase. (2) electrodialysis does not change the concentrations of Ni2+, Co2+ and Mn2+ ions significantly, but chemical precipitation could reduce Ni2+ and Co2+ ions to less than half of their initial values. Through electro-dialyzing the leachate, the H2 evolution reaction mechanism was found to switch from the Volmer-acid Heyrovsky mechanism to the Volmer-alkaline Heyrovsky mechanism at a pH of around 3.7.

Ionic liquids (ILs) nanostructuring at electrified interfaces is of both fundamental and practical interest as these materials are increasingly gaining prominence in energy storage and conversion processes. However, much remains unresolved about IL potential-controlled (re)organization under highly polarized interfaces, mostly due to the difficulty of selectively probing both the distal and proximal surface layers of adsorbed ions. In this work, the structural dynamics of the innermost layer (<10 nm from the surface) were independently interrogated from that of the ionic layers in the sub-surface region (>100 nm from the surface), using an infrared (IR) spectroscopy approach. By tuning the metal fill factor of gold films deposited on conductive metal oxide-modified IR internal reflection elements, the charge-driven (re)structuring of the inner and distal layers of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate is unveiled. Within a relatively wide potential region (∼±1 V) bounding the potential of zero charges, the ionic liquid is shown to undergo a reversible (i.e., soft) reorganization whereby the innermost layer of anions (cations) is exchanged by a layer of cations (anions). Kinetically unhindered changes in the number density of constituent cations and anions largely follow electrostatic expectations in the subsurface region, whereas the innermost layer exhibits a pronounced hysteresis and very slow relaxation. Under larger negative potential bias, IL restructuring is characterized by a highly irreversible (i.e., hard) and intense interfacial densification of the BMPy+ cations, consistent with the formation of nanoscale segregated liquids. The outcomes of this work reveal a plastic IL nanostructuring under a strong electric field.

To understand the speciation of solutes in aqueous solutions in high temperature radiation environments, we report the design and fabrication of a custom-built, high temperature (≤300 °C) titanium irradiation cell with in situ optical spectroscopy capabilities, as afforded by coupled fiber optic cables. The wetted surfaces of the 8-inch tall cylindrical cell with 3.5 in. diameter are entirely made of titanium, sapphire, and gold, which are chemically and radiolytically inert. The initial benchmarking results are reported, including the baseline spectrum of deionized water as a function of temperature, the stability of a spectrum over 4 h at 100 °C, and an irradiated Fricke dosimetry solution under ambient irradiator temperature conditions (27.0 ± 0.5 °C). The average gamma radiation dose rate in the cell in its current configuration is 26.1 ± 1.3 Gy min−1. This cell has application in studying several processes throughout the nuclear fuel cycle, including the reactor coolant behavior.

The electrolyte in spent Li-ion batteries is prone to cause a high risk of hazardous emissions (HF, etc.) in the state-of-the-art recycling processes. It is the main source of fire risks and represents a significant burden for the recyclers due to the safety. Still, extended research to fully recycle the electrolyte without its destruction at elevated temperature is scarce. This study focuses on the electrolyte extraction from spent LiBs using sub- and supercritical carbon dioxide to fill this gap. The effects of the critical process parameters, pressure (60–120 bar), temperature (15–55 °C) and extraction time (1–50 min) from spent pouch cells were investigated. The results showed that the CO2 density, which is related to pressure and temperature, is significant for the recovery of the non-polar electrolyte solvents. The most important outcome is that dimethyl carbonate, and ethyl methyl carbonate were fully selectively extracted at the studied conditions, whereas the polar ethylene carbonate was extracted only in trace amounts. As results indicated, LiPF6 did not decompose in the proposed process whereby the toxic-gas emissions were dramatically minimized compared to the state-of-the-art recycling processes.

Rare earth elements (REEs) are a class of critical materials vital to an array of applications such as electronics, batteries, and defense weapons systems. These elements coexist in minerals and ores, and due to their similar chemical properties, the challenge remains to find an effective means of separation. Current large-scale separation processes rely on slight differences in size and acidity between REEs, however these separations are inefficient and pose detrimental risks to the environment due to the large volumes of volatile organics and acids required to achieve separations. REEs can be separated on the basis of their migration under an applied electric field, i.e., their electrophoretic mobility, which depends on differences in size and charge and may be modified through coordination with ligands. The degree to which coordination with ligands may influence the transport properties of these metal-ligand systems remains, for the most part, unknown. Here, we investigate the fundamental transport properties of a series of REE-carboxylate ligand complexes in aqueous solution via capillary electrophoresis and molecular dynamics (MD) simulations are carried out to validate metal-ligand coordination geometry and diffusion properties. Iminodiacetic acid (IDA) is identified as a ligand that greatly enhances separation between light and heavy lanthanides by selectively coordinating with light lanthanides in a tridentate mode and heavy lanthanides in a bidentate mode.

In situ investigations of electrocatalytic processes of increasing societal interest such as the nitrogen reduction reaction (NRR) require aggressive experimental conditions that are not readily compatible with surface sensitive techniques such as attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). A method for performing ATR-SEIRAS studies at very negative potentials where conventional IR-active films delaminate and fail is reported. The method relies on a thin film of very robust boron-doped diamond deposited on a micromachined Si wafer, which provides extended mid-IR transparency at long wavelengths. SEIRAS activity is achieved by electrodepositing gold nanoparticles onto the conductive BDD layer. The Au@BDD layers are shown to sustain prolonged periods of electrolysis at negative potentials, with no degradation of the modifying layer. The efficacy of these substrates for electrocatalysis is demonstrated by studying the reduction of N2 at -1.5 V vs Ag/AgCl in an aqueous-based electrolyte. Under these conditions, direct spectroscopic evidence of both NH3 and hydrazine formed from the nitrogen reduction reaction (NRR) is provided.

Chromium ions can make their way into the primary coolant of nuclear power reactors from the corrosion of stainless-steel reactor components, decreasing the material's corrosion resistance and resulting in increased transport of further corrosion products. Despite these potential effects, the radiation-induced redox speciation of chromium ions in aqueous solution is not well understood, especially at the elevated temperatures experienced by reactor coolants. In the present work, we report new experimental results demonstrating that in aerated aqueous solution, the radiolytic oxidation of Cr(III) to Cr(VI) occurs at pH 4, while the reduction of Cr(VI) to Cr(III) occurs at pH 2. The oxidation of Cr(III) is primarily attributed to the reaction of the hydroxyl radical (˙OH) with the Cr(OH)2+ species, while the reduction of Cr(VI) is attributed to reactions involving the hydrated electron (eaq-) and hydrogen atom (H˙). Additionally, the steady-state equilibrium yield of Cr(VI) from the gamma irradiation of pH 4 Cr(III) solutions decreased with increasing temperature (over a range of 37-195 °C). This observation indicates that the activation energy of the Cr(VI) reduction reactions is higher than that for the Cr(III) oxidation reactions, such that it becomes relatively more favorable at higher temperatures. Overall, these data are important for the development of complementary multiscale models for the prediction of metal ion speciation in high temperature radiation environments.

Waste streams from the incineration of metal-containing materials like such as computer processor boards and batteries may contain critical rare earth elements like praseodymium. Data on the solubility of Pr compounds and on their distribution coefficients in supercritical CO2/ionic liquid two-phase systems are important to determine if an ionic liquid/supercritical CO2 two-phase approach is feasible toward the recovery of a particular metal. This work provides data on the solubility of various praseodymium compounds in butyl-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyTf2N) ionic liquid and on the distribution coefficients of these praseodymium compounds in the supercritical CO2 phase of the two-phase BMPyTf2N ionic liquid/supercritical CO2 system, with and without a tributyl phosphate additive.

Circularizing end of life products such as electronic waste can open a new source for rare earth elements (REEs) that will decrease the demand pressure on conventional virgin production. The last step to produce REEs consists of a refining process to convert rare earth oxide (REO) to REE metal. One promising technology is processing REO via a room temperature ionic liquid, which is characterized by low energy requirements in contrast to existing REEs extraction processes. In this work, life cycle and techno-economic assessments are performed and compared against molten salt electrolysis. The results show that both processes have advantages and disad-vantages in terms of environmental performance, and that they are similarly competitive in terms of economic performance. A breakeven analysis suggests that future research should focus on coupling the production of REOs with the refining processes to attempt to lower REO cost and make them economically feasible in the U.S.

The viscosity, conductivity, electrochemical window and related thermodynamic properties such as excess volume and dynamic viscosity deviation of two phosphonium ionic liquids were measured and calculated for "as-supplied" and dried neat liquids and also v/v mixtures of 99/1, 95/5, 90/10, 75/25, and 50/50 of the ionic liquids with propylene carbonate (PC). Tetradecyltrihexylphosphonium dicyanamide ([P-6,P-6,P-6,P-14](+)dicyanamide), Cyphos 105, and tetradecyltrihexylphosphonium bis(trifluororomethane sulfonyl)imide (called bistriflimide) ([P-6,P-6,P-6,P-14](+)bistriflimide), Cyphos 109, ionic liquids were studied. Generally speaking, there were slight differences in the measured properties of the wet and dried IL solutions which were reflected in differences if the calculated properties. The measured and calculated properties were compared with those collected and derived from a piperidinium-based ionic liquid, methylpropyl piperidinium bistriflimide. Arrhenius plots for both the viscosity and conductivity were linear, with the linearity of the Litovitz plots being slightly higher. The viscosity and conductivity of the phosphonium solutions yielded Walden Plots that differed from Walden plots of piperidinium solutions and other ionic liquid solutions. For the phosphonium based ionic liquids, the ionicity was found to increase with increasing dilution in propylene carbonate. The electrochemical windows of the ionic liquids were determined as a function of the concentration of the ionic liquid present in the solution. The size of the window generally initially decreased and then increased with the addition of PC for the [P-6,P-6,P-6,P-14](+)dicyanamide ionic liquid increasing from 3.4 V in the 95/5 v/v (volume Cyphos 105) to volume of PC solvent) to 3.7 in the 50/50 dried IL case. The electrochemical windows of the dried liquids were slightly larger 3.5 V for the 95/5 v/v and 4.2 V for the 50/50 v/v Cyphos 105/PC solutions. The electrochemical window was larger and the conductivity was higher for the piperidinium IL solutions, but since the ionicity increases with dilution, the phosphonium based IL solutions may prove favorable for processes such as electrochemical reduction. (C) 2022 Elsevier B.V. All rights reserved.

The electrochemical production of rare earth metals (REMs) in ionic liquids (ILs) has received much attention as a promising, sustainable replacement to molten salt electrolysis. Water additives have been suggested as a promoting strategy for the ionic liquid process; however, the fundamental understanding of the interfacial processes required to assess the overall viability for REM production is lacking. In this regard, a full investigation of the impact of water on dysprosium (Dy) electrodeposition in pyrrolidinium triflate (BMPyOTf) ionic liquid was carried out. Water introduction was revealed to involve an interplay of implications on the electrodeposition process, including coordination, speciation, reduction pathways, interfacial dynamics, nucleation, and metal stability and purity. Under highly dry conditions, the reduction occurs at a very negative potential (-3.3 V) in a consecutive pathway, resulting in negligible metal electrodeposition (low rate and efficiency) at the electrode surface. Small water concentrations (<500 ppm) lead to partitioning of the Dy complex between water and IL-coordinated speciation, giving rise to an additional wave at a more positive potential (-2.4 V). Probing the heterogeneous Dy speciation by spectroscopic analyses enabled uncovering of the reduction mechanism and evaluation of the mass transport properties. In addition to lowering the reduction thermodynamics, water introduction also improved the nucleation, deposition rate, and faradic efficiency. Despite these benefits, stripping voltammetric analysis predicts substantial chemical reactivity of the deposited Dy metal with water additives and/or electrolyte components, under long timescales. Surface characterization of the obtained product confirmed the instability of Dy metal as an oxidized/fluorinated material and its limited purity (similar to 60%). Moreover, high water introduction triggered a fast hydrogen evolution reaction (HER), downgrading the robustness of system efficiency. The overall impact of water additives seems to engender both promoting and mitigating effects on electrochemical REM production in IL, requiring a specific technoeconomic assessment and/or more innovative strategies to be sought.

Deep decarbonization of major industries such as metals manufacturing requires extensive process integration and controls to manage feedstocks, side reactions, heat, water, and waste streams. The scale of the energy and capital investment requires that process integration be validated to a high level of confidence with no bias. Industries such as steel production have very thin profit margins. Therefore, lack of confidence in process integration, product quality, and economics is a major deterrence to changes in manufacturing capital investment. Public sector investment in reconfigurable pilot testbeds and a first-of-a-kind plant would be necessary to de-risk technical and financial barriers prior to industry-wide buildout. DOE should consider a National Lab-led hub for the testbeds. Lab testbeds could be utilized in campaigns and allow multiple industrial partners to evaluate and validate technologies prior to making major capital investments.

The 2020 Materials for Harsh Service Conditions (M4HSC) Workshop was coordinated by three different U.S. Department of Energy (DOE) Offices: the Advanced Manufacturing Office (AMO), the Office of Fossil Energy (FE), and the Office of Nuclear Energy (NE). The event was held virtually October 27–30, 2020. The workshop brought together stakeholders from academia, industry, national laboratories, and DOE offices to identify the opportunities (paths for obtaining desirable goals), challenges (actionable tasks taken up along these paths), barriers (obstacles impeding advancement along the paths), and research and development (R&D) needs for enabling development of technology readiness level (TRL) 3–6 materials and materials systems, as well as their advancement into widespread commercial application.

Electrochemical reduction of rare earth elements (REEs) in ionic liquids (ILs) has attracted much attention, as a promising low temperature and alternative technology for molten salt electrolysis. While reported studies have established the proof of concept of the ionic liquid technology, efficient recovery and fundamental understanding of the electrodeposition process in these systems are still lacking. In this work, the reduction of dysprosium triflate (Dy(OTf)(3)) complex is investigated in neat pyrrolidinium triflate (BMPy-OTf) ionic liquid, a commercial but poorly explored system in literature. Chronoamperometry and surface characterization (SEM-EDS, XPS and ICP-MS) demonstrated an efficient (similar to 80%) electrochemical recovery of Dy metal, with deposition rates approaching 10 mg.h(-1).cm(-2) at 0.3 M metal concentration, small applied potentials (similar to-3 V Fc(+)/Fc) and ambient temperature (25 degrees C). Cyclic voltammetry revealed two main electrodeposition waves (Red1 and Red2), suggesting single 3e- reduction of two co-existent metal complexes with different coordination spheres, strongly (Red2) and weakly (Redl ) coordinated metal complex with the ionic liquid triflate anions. This suggestion was supported by the vibrational (Mid-IR) analysis, where downshifts of the nu(as)(SO) stretching mode were consistent with an evolution of weaker metal coordination at higher concentrations. Near-IR confirmed the evolution of speciation, from one main complex at low concentrations to a mixture of species at higher concentrations. Estimation of the speciation's distribution from deconvoluted NIR and semi-derivative traces indicated that voltammetric currents are controlled by bulk concentrations. While under coulometric conditions, the metal reduction seems to proceed via the IL-coordinated thermodynamics, due to enhanced anion concentrations at the electrochemical interface. Extended study to bistriflimide analogue systems revealed a distinct infrared signature for the IL-coordination and validated the correlation between the observed reduction processes and the speciation heterogeneity in these systems. The outcomes of this work demonstrate an efficient electrochemical recovery of Dy in triflate-based systems, while shedding the light on the impact of solvation and coordination interplays on the electrodeposition process of REEs in ionic liquids. (C) 2021 Elsevier Ltd. All rights reserved.

This report identifies seven high-priority, crosscutting research directions for energy-producing and energy-intensive industries in which harsh service environments are experienced.Electrical power-generating technologies that could benefit include nuclear, renewable (e.g., wind, solar thermal, geothermal, and hydro), and combustion processes (e.g., hydrogen, natural gas, biomass, and coal).Investment in these research areas could drive deployment of new materials and manufacturing innovations that would, in turn, enable widespread implementation of advanced materials into the energy production and manufacturing sectors, leading to stepchanges in materials systems' performance and manufacturing efficiency.Those technological step-change advancements would stimulate and reinvigorate domestic manufacturing, improve U.S. manufacturing competitiveness, markedly improve energy efficiency in targeted energyintensive manufacturing processes, and enable practice of technologies that reduce the carbon footprint across a broad swath of manufacturing and electricity production supply chains.The 2020 Materials for Harsh Service Conditions (M4HSC) Workshop was coordinated by three different U.S. Department of Energy (DOE) Offices: the Advanced Manufacturing Office (AMO), the Office of Fossil Energy (FE), and the Office of Nuclear Energy (NE).The event was held virtually October 27-30, 2020.The workshop brought together stakeholders from academia, industry, national laboratories, and DOE offices to identify the opportunities (paths for obtaining desirable goals), challenges (actionable tasks taken up along these paths), barriers (obstacles impeding advancement along the paths), and research and development (R&D) needs for enabling development of technology readiness level (TRL) 3-6 materials and materials systems, as well as their advancement into widespread commercial application.The purpose of the workshop was to identify data gaps, R&D needs, technology challenges, and fabrication• More Data: Data-driven materials/system testing approaches that lead to more accurate prediction of materials behavior and materials properties under harsh service conditions at relevant timescales• Accelerated Testing and Qualification: Reduced time to market for improved materials systems through accelerated testing and qualification• Improved Manufacturing Methods: Methods and capabilities that are advanced, adaptable, agile, smart, and more efficient• Greater Understanding: Improved understanding of advanced manufacturing process fundamentals, control parameters, and subsequent effects on materials properties• Smart: Improved in situ process monitoring technologies, including sensors, modules, and packaging that can be embedded inside furnaces, downhole wells, reactors, and other extreme environments to provide valuable real-time data for utilization in process monitoring and control• Access: Access to capabilities through publicly available facilities• Improved Materials: Improvements in material performance for essentially every harsh service condition in which either power generation or energy-intensive processes are employed Figure ES-1.