MaxPower (United States)

REBCO (rare-earth barium copper oxide) coated conductor tapes are a highly attractive option for magnet materials in future tokamak fusion power plants. However, the threat of intense neutron and gamma radiation, together with AC losses during magnet coil ramping, has raised concerns around magnet coil lifetimes. Irradiation-induced changes to flux creep rate has been identified as a key performance-limiting factor in REBCO tapes at low temperatures and high fields post-irradiation with gamma rays; spontaneous flux creep contributes to hysteretic AC loss in REBCO cables under applied AC fields. Knowing that multi-filamentary tapes are under consideration for tokamaks as an AC loss mitigation, magnetic measurements and gamma irradiation experiments are presented here on striated and mono-filamentary YBCO tapes to investigate the differences in post-irradiation screening currents and AC losses. Reduction in AC losses improved magnetisation critical current density (Jc) retention after 1 MGy in the multi- relative to the mono-filamentary samples. After the 5 MGy dose, striations then made the multi-filamentary tape more susceptible to Jc degradation because of the thinner individual filament width. Scanning transmission electron microscopy analysis on an analogous GdYBCO mono-filamentary tape did not indicate the introduction of nm-scale amorphisation to the active GdYBCO layer after gamma irradiation. A potential theoretical explanation for the underlying mechanism altering the flux-pinning landscape across the REBCO layer surface in gamma-irradiated tapes is discussed. This work concluded that gamma effects on screening current capability should be considered in future tokamak REBCO tape qualification studies.

Ever increasing demand on high energy density batteries positions sulfur as a very promising cathode material for next-generation energy storage due to its high theoretical capacity of 1675 mAh/g. Electronically sulfur is highly insulating, and therefore integration of a conducting framework such as a carbon nanotube (CNT) scaffold with sulfur is a key aspect of the cathode design. Despite numerous efforts dedicated to S-CNT cathode development, increasing sulfur loading to above 1 mg/cm2 while maintaining the cycling stability of the Li–S cell remains challenging. This could be partly due to the lack of understanding of the spatial distribution of sulfur in the CNT matrix and its location with respect to the morphology of the CNT scaffold. We demonstrate herein that the sulfur has a hierarchical distribution in the CNT cathode at high sulfur loading (>5 mg/cm2) spanning multiple length scales (from nanometer to submillimeter). Sulfur infiltration into the CNT rather than the sulfur loading plays a key role in determining the redox reaction kinetics, Li+ ion diffusion, and the galvanostatic cycling capacity and stability of Li–S cells. This study provides new insights for the design and fabrication of high loading, binder-free sulfur–carbon-based cathode architectures for next-generation high energy Li–S batteries.

This chapter deals specifically with aqueous systems, including the novel Li—seawater battery. Theoretical energies and capacities for selected metal—air systems were calculated from critically evaluated Gibbs energies. The chapter highlights the present-day advances in the development of aqueous Li—air (Li—O2) cells and batteries, to identify areas for future research and development. It summaries the technical areas that require advanced R&D for a commercially viable Li—air battery. The chapter also deals with mechanisms in acid and alkaline solutions, the nature of carbon materials and catalysts, and pressure and temperature. It focuses on protected lithium anode approaches. The selection of an electrolyte solution is generally governed by several factors, such as electrolyte solution conductivity, oxygen solubility in the electrolyte solution, stability of the Li ion—conducting glass ceramic (LiC-GC) membrane in the various electrolyte solutions, and possible precipitation of reaction products upon cell discharge.

Lithium-air (Li-air) batteries have a much higher theoretical energy density than conventional lithium batteries and other metal air batteries, so they are being developed for applications that require long life. Water vapor from air must be prevented from corroding the lithium (Li) metal negative electrode during discharge under ambient conditions, i.e., in humid air. One method of protecting the Li metal from corrosion is to use an oxygen selective membrane (OSM) that allows oxygen into the cell while stopping or slowing the ingress of water vapor. The desired properties and some potential materials for OSMs for Li-air batteries are discussed and the literature is reviewed.

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Techniques for implementing stabilized lithium metal powder (Lectro® Max Powder 150, SLMPTM) as a surface application onto mesocarbon cathodes have been studied. These techniques included dip coating, draw-down coating and spray coating already prepared electrodes in a dry room environment. This testing resulted in electrodes that demonstrated a reduced apparent loss, which has the potential to improve the overall capacity of commercial cells. Of these three techniques, spray coating was determined to be the most applicable method of depositing the SLMPTM onto the coating with appropriate precision. More specifically, a low volume, low pressure off-the-shelf sprayer with a standard modification to replace the PTFE seals with polyethylene seals could be used to spray the coating to the proper loading. With proper mixing techniques, large numbers of electrodes could be sprayed with one batch of SLMPTM slurry, allowing eventually for larger prismatic lithium ion cells to be developed.