Spinel vanadium oxides are a promising material for electrochemical studies because they have been shown to cycle Mg 2+ ions at capacities higher than their Mn and Cr-doped counterparts [1]. These highcapacity nanocrystals are typically on the order of a few nm in radius and thus present challenges to studies using electron microscopy techniques. As part of this contribution, we will show that elevating the thermal annealing temperature during synthesis significantly increases the size of MgV2O4 crystals and improves their crystallinity. This has opened the way for studies focused on understanding electrochemical activity in single particles. Here, we will present a study concentrating on the role of crystal surface types to electrochemical activity in MgV2O4 crystals using atomic-resolution scanning transmission electron microscopy (STEM) and electron-probe spectroscopy techniques.

This study will be conducted using an aberration-corrected cold field emission JEOL ARM200CF operated at 200kV primary electron energy. Imaging and spectroscopic measurements will be conducted with the emission current at 15μA. The electron probe will be operated at 24 mrad convergence semiangle and the inner angle detector will be set to 75 mrad for high angle annular dark field imaging and 30mrad for low angle annular dark field imaging. The microscope is also equipped with an Oxford XMAX100TLE X-ray detector and a post-columns Gatan Continuum GIF spectrometer. Beam induced structural changes to the unoccupied density of states will be tracked with LIVE EELS beta software from Gatan.