Investigation of MgV₂O₄ as a Cathode Material for Multivalent Ion Batteries Using Atomic Resolution Electron Microscopy

Nanocrystal spinel vanadium oxides are promising candidate materials for post lithium rechargeable batteries. Recent reports demonstrate that, despite the presence of complex structural defects, V₂O₄ nanocrystals are capable of cycling Mg²⁺ at capacities greater than Cr and Mn spinel counterparts ^[1]. In this contribution, we will present a characterization of spinel MgV₂O₄ using atomic resolution scanning transmission electron microscopy (STEM) techniques, such as nanoscale electron energy loss measurements (EELS) and x-ray energy dispersive spectroscopy (XEDS) elemental determination. As part of our analysis, we will explore the effects that crystal size and structural defects have on electrochemical cycling performance. We will demonstrate that nanocrystalline particles (~5nm in diameter) react entirely upon electrochemical cycling, while activity in larger crystals is typically confined to a thin surface layer.  Using nanoscale EELS measurements, we will measure variability in electrochemical activity between individual particles as well as locally within larger single crystals.

 

^[1] Hu, L., Jokisaari, J. R., Kwon, B. J., Yin, L., Kim, S., Park, H., ... & Cabana, J. (2020). High Capacity for Mg2+ Deintercalation in Spinel Vanadium Oxide Nanocrystals. ACS Energy Letters, 5(8), 2721-2727.