The deployment of nonaqueous redox flow batteries for grid-scale energy storage has been impeded by a lack of electrolytes that undergo redox events at as low (anolyte) or high (catholyte) potentials as possible while exhibiting the stability and cycling lifetimes necessary for a battery device. Herein, we report a new approach to electrolyte design that uses physical organic tools for the predictive targeting of electrolytes that possess this combination of properties. We apply this approach to the identification of a new pyridinium-based anolyte that undergoes 1e electrochemical charge-discharge cycling at low potential (-1.21 V vs Fc/Fc) to a 95% state-of-charge without detectable capacity loss after 200 cycles.

Recent efforts have led to the design of new anolytes for nonaqueous flow batteries that exhibit reversible redox couples at low potentials. However, these molecules generally cycle through just a single electron-transfer event, which limits the overall energy density of resulting batteries on account of the undesirably high equivalent weight (i.e., ratio of anolyte/supporting electrolyte molecular weight to electrons transferred). In addition, these anolytes generally require expensive alkylammonium salts as supporting electrolytes for stable cycling, which further increases the equivalent weight of the system. The current work describes the multielectron redox cycling of a low-potential anolyte using alkali metal salts as supporting electrolytes. These studies reveal that potassium hexafluorophosphate (KPF6) dramatically lowers the equivalent weight of the anolyte system while supporting flow cell cycling through two redox events at low potentials for 150 cycles with no detectable degradation.

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One new and nine explanted zirconia femoral heads were studied using glancing angle X-ray diffraction, scanning electron microscopy, and nanoindentation hardness techniques. All starting zirconia implants consisted only of tetragonal zirconia polycrystals (TZP). For comparison, one explanted alumina femoral head was also studied. Evidence for a surface tetragonal-to-monoclinic zirconia phase transformation was observed in some implants, the extent of which was varied for different in-service conditions. A strong correlation was found between increasing transformation to the monoclinic phase and decreasing surface hardness. Microscopic investigations of some of the explanted femoral heads revealed ultra high molecular weight polyethylene and metallic transfer wear debris.