Interfacial Engineering with a Nanoparticle-Decorated Porous Carbon Structure on ß″-Alumina Solid-State Electrolytes for Molten Sodium Batteries.

We present a novel anode interface modification on the ß″-alumina solid-state electrolyte that improves the wetting behavior of molten sodium in battery applications. Heat treating a simple slurry, composed only of water, acetone, carbon black, and lead acetate, formed a porous carbon network decorated with PbOx (0 ≤ x ≤ 2) nanoparticles between 10 and 50 nm. Extensive performance analysis, through impedance spectroscopy and symmetric cycling, shows a stable, low-resistance interface for close to 6000 cycles. Furthermore, an intermediate temperature Na-S cell with a modified ß″-alumina solid-state electrolyte could achieve an average stable cycling capacity as high as 509 mA h/g. This modification drastically decreases the amount of Pb content to approximately 3% in the anode interface (6 wt % or 0.4 mol %) and could further eliminate the need for toxic Pb altogether by replacing it with environmentally benign Sn. Overall, in situ reduction of oxide nanoparticles created a high-performance anode interface, further enabling large-scale applications of liquid metal anodes with solid-state electrolytes.

The evolution of hydrated lime-based cementitious waste forms during leach testing leading to enhanced technetium retention.

The interaction between radionuclides and cementitious material phases is crucial in the prediction of the long-term disposal behavior of cementitious waste forms. This work focuses on the behavior of technetium-99 (Tc) within a hydrated-lime based waste form developed as a candidate to immobilize high-sulphate containing liquid wastes known to inhibit cement solidification when using a fly ash based formulation. In leach testing, the hydrated-lime based formulation demonstrated improvement in Tc retention over a fly ash containing formulation beginning after 14 d leaching. The mineralogical evolution of the hydrated-lime samples during leach testing showed a decrease in portlandite content and reduction capacity at the onset of the Tc retention improvement. Leach testing upwards of 400 days showed the improved Tc retention was sustained. Samples cured for different lengths of time (28 days vs 60 days) confirmed that the improved Tc retention and mineralogic change was caused by cement - leachant interactions and not the sample curing time. The Tc observed diffusivities in the hydrated-lime samples are amongst the lowest measured in a cement waste form tested for development at the US Department of Energy Hanford site, leading to a possible pathway to improved cement conditioning where contaminants can be retained for long disposal times.

Role of Zeolite Structural Properties toward Iodine Capture: A Head-to-head Evaluation of Framework Type and Chemical Composition.

This study evaluated zeolite-based sorbents for iodine gas [I2(g)] capture. Based on the framework structures and porosities, five zeolites, including two faujasite (FAU), one ZSM-5 (MFI), one mesoMFI, one ZSM-22 (TON), as well as two mesoporous materials, were evaluated for I2(g) capture at room temperature and 150 °C in an iodine-saturated environment. From these preliminary studies, the three best-performing zeolites were ion-exchanged with Ag+ and evaluated for I2(g) capture under similar conditions. Energy-dispersive X-ray spectroscopy data suggest that Ag-FAU frameworks were the materials with the highest capacity for I2(g) in this study, showing ∼3× higher adsorption compared to Ag-mordenite (Ag-MOR) at room temperature, but X-ray diffraction measurements show that the faujasite structure collapsed during the adsorption studies because of dealumination. The Ag-MFI zeolites are decent sorbents in real-life applications, showing both good sorption capacities and higher stability. In-depth analyses and characterizations, including synchrotron X-ray absorption spectroscopy, revealed the influence of structural and chemical properties of zeolites on the performance for iodine adsorption from the gas phase.

Probing the Radial Chemistry of Getter Components in Light Water Reactors via Controlled Electrochemical Dissolution.

Getters are among the key functional components in the tritium-producing burnable absorber rods (TPBARs) of light water reactors (LWRs) and are used to capture the released tritium gas. They are nickel-plated zircaloy-4 tubes that, upon exposure to irradiation or tritium in the light water reactors, undergo alteration in structure, chemical composition, and chemistry. Understanding the radial tritium distribution is key to gaining insight into the evolution of new chemistry upon irradiation to predict getter performance. The holy grail is to develop a method akin to selectively peeling off the layers of an onion in an effort to get a radial map of elements and particularly tritium across the getter. Toward this goal, the overall aim of this work is to establish a correlative technique that can be used to determine radial tritium distribution across getters. To this end, this work specifically focuses on the validation of a correlative method for controlled radial dissolution of nickel-plated getters. Here, pristine getters as well as getters loaded with different mass ratios of hydrogen and deuterium are used as the nonradioactive surrogates of tritium, the idea being that the methodology can be readily extended to tritiated getter components. Here, the surface nickel layers as well as the bulk zirconium layers are sequentially dissolved in a controlled, uniform way using voltage-assisted electrochemical dissolution techniques. The dissolution is complemented by periodic elemental analysis of the electrolyte solution during and post dissolution. This is complemented by microscopic analyses on the exposed surfaces to provide a correlative technique for a complete picture of the radial distribution of various elements across the getter.

An electrochemical technique for controlled dissolution of zirconium based components of light water reactors.

Zircaloy-4 (Zr-4) based liners and getters are the principle functional components of Tritium-Producing Burnable Absorber Rods (TPBARs) in light water nuclear reactors where they reduce tritiated water into tritium gas. Upon tritium exposure, zirconium tritide is formed, which changes the chemical composition, structure and morphology of these materials. Their thermodynamic properties are affected by (i) the hydride phase identity, (ii) radial and spatial tritide/hydride (T/H) distribution, and (iii) the changes in structure and morphology of the material upon T/H-migration, and their comprehensive knowledge is needed to predict performance of these materials. This work demonstrates that controlled potential electrochemistry techniques to be highly efficient for controlled oxidative radial dissolution of Zr-4 based liners (both unloaded and loaded with hydride/deuteride as chemical surrogates for tritium). The electrodissolution is further combined with microscopic techniques to accurately determine the distribution of hydride phases. This work demonstrates a reliable technique for radially etching the liners after irradiation to provide insight into the radial and spatial distribution of tritium within the TPBAR, improving the fundamental understanding of tritium transport and providing a basis for validating predictive models.

An Intermediate-Temperature High-Performance Na-ZnCl2 Battery.

The Na-ß-alumina battery (NBB) is one of the most promising energy storage technologies for integrating renewable energy resources into the grid. In the family of NBBs, Na-NiCl2 battery has been extensively studied during the past decade because it has a lower operating temperature, better safety, and good battery performance. One of the major issues with the Na-NiCl2 battery is material cost, which is primarily from Ni metal in the battery cathode. As an alternative, Zn is much cheaper than Ni, and replacing Ni with Zn in the cathode can significantly reduce the cost. In this work, we investigate the performance and reaction mechanism for a Na-ZnCl2 battery at 190 °C. Two-step reversible reactions are identified. During the first step of charging, NaCl reacts with Zn to produce a ribbon-type Na2ZnCl4 layer. This layer is formed at the NaCl-Zn interface rather than covering the surface of the Zn particles, which leads to an excellent cell rate capability. During the second step, the produced Na2ZnCl4 is gradually consumed to form ZnCl2 on the surface of Zn particles. The formed ZnCl2 covers most of the surface area of the Zn particles and shows a limited rate capability compared to that of the first step. We conclude that this limited performance of the second step is due to the passivation of Zn particles by ZnCl2, which blocks the electron pathway of the NaCl-Zn cathodes.

Advanced Na-NiCl2 Battery Using Nickel-Coated Graphite with Core-Shell Microarchitecture.

Stationary electric energy storage devices (rechargeable batteries) have gained increasing prominence due to great market needs, such as smoothing the fluctuation of renewable energy resources and supporting the reliability of the electric grid. With regard to raw materials availability, sodium-based batteries are better positioned than lithium batteries due to the abundant resource of sodium in Earth's crust. However, the sodium-nickel chloride (Na-NiCl2) battery, one of the most attractive stationary battery technologies, is hindered from further market penetration by its high material cost (Ni cost) and fast material degradation at its high operating temperature. Here, we demonstrate the design of a core-shell microarchitecture, nickel-coated graphite, with a graphite core to maintain electrochemically active surface area and structural integrity of the electron percolation pathway while using 40% less Ni than conventional Na-NiCl2 batteries. An initial energy density of 133 Wh/kg (at ∼C/4) and energy efficiency of 94% are achieved at an intermediate temperature of 190 °C.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density.

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium-nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg(-1), higher than that of conventional tubular sodium-nickel chloride batteries (280 °C), is obtained for planar sodium-nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium-nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.