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Lithium-ion batteries are prone to failure at low temperatures and dendrite growth during charging is one suspect. We attempt to understand lithium dendrite growth by observing their number, initiation time and growth rate at ambient and sub-ambient temperatures: [?]10degC, 5degC, and 20degC using an in-situ optical microscopy cell (Li0|Li0). We find that while dendrites initiate quickly at [?]10degC, the cells at 5degC short-circuit most rapidly due in part to a favorable morphology at this temperature. The experimental approach has broad applicability to other electrochemical energy storage technologies where mass transport limitations are present at low temperatures, particularly Li-air, Li-S, and Zn-air batteries.

The ORR on Pt in an alkaline electrolyte is studied for the impact of support effects. Platinum nanoparticles are supported on nanoscale tantalum oxyphosphate or tantalum oxide films on Vulcan carbon (VC) to make either Pt/[TaOPO4/VC] or Pt/[Ta2O5/VC] electrocatalysts, which were then characterized with BF-STEM. Their ORR activity was determined by RDE methodology in 0.10 M KOH electrolyte. The Pt mass activities of the Pt/[TaOPO4/VC] and Pt/[Ta2O5/VC] electrocatalysts are both approximately 250 mA mgPt[?]1 at 0.925 V, or about 2 x greater than that of a commercial Pt/VC electrocatalyst (120 mA mgPt[?]1), implying a substantial effect of the Ta-based support films.