Multivalent rechargeable batteries have often been considered a natural successor to traditional lithium-ion technology. Replacing Li+ with a divalent ions, such as Mg2+, Ca2+, or Zn2+ could enable the use of a metal anode and potentially double the specific capacity of the cathode. Research into suitable high voltage cathodes and electrolytes has focused on oxide materials that show reversible multivalent ion intercalation at room and elevated temperatures. While many oxide lattice structures are typically assumed to exhibit poor bulk Mg-ion mobility recent theoretical and experimental studies have shown that oxide spinels can have high Mg ion mobility in the bulk. Questions about possible interfacial transport bottleneck still remain unanswered. In this presentation, I will provide on review our ongoing studies of several multi-valent ion cathode materials, including MgV2O4, Ca-FePO4, and CaMnOx. Specifically, I will show how atomic-resolution scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS) in conjunction with in-situ liquid-cell microscopy can be used to study the intercalation and degradation mechanisms of various oxide materials. New high-temperature electro-chemical in-situ liquid cell TEM measurements will be introduced to examine the mechanisms underlying the observed structural transitions during Mg2+ intercalation into layered vanadium oxide at 110°C with high capacity. Furthermore, the use of model systems, including single-crystal thin film materials grown by molecular-beam epitaxy with well-defined surface terminations to answer questions about interfacial transport will also be discussed.

Atomic-resolution and In-Situ analysis of multi-valent ion battery cathodes

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ACS Fall 2022

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