(4ai) In Situ Microscopic Characterization of Energy Materials for Grid-Scale Storage

Batteries are designed to maximize interfacial area by employing thick, porous electrodes, which can display nonhomogenous reaction conditions. Non-electrochemical Information (microscopy, diffraction, etc) is needed to characterize localized, microscopic phenomena within cycling batteries. This can involve either model experimental systems or powerful cell-penetrating techniques such as energy dispersive X-ray diffraction (EDXRD).

In this presentation I report in situ EDXRD data collected on cycling LR20 Zn-MnO2 batteries using white beam X-rays at the National Synchrotron Light Source (NSLS) located at Brookhaven National Lab. This data reveals transient zinc oxide layers that form and dissolve at the anode-separator interface during cycling, as a function of battery discharge rate. This is found to be a cause of battery failure in some cases when the battery has reached hundreds of cycles.

This is important because it is generally recognized that electrochemical storage on a large scale is desirable for a number of societal reasons including the smart grid and solar cell integration. For applications with critical cost and environmental restrictions the Zn-MnO2 alkaline chemistry is well-suited. My work is broadly focused on inexpensive ways to accomplish grid-scale storage.

Additionally, the statistical aspect of batteries is often overlooked in academia. Batteries are deterministic systems, but during long cycling lifetimes battery fade and failure are subject to contingency, nucleating events, and other phenomena that must be treated statistically. Said more plainly, batteries often fail due to their materials, but even a simple battery can fail more than one way. EDXRD results confirm this and provide a way to quantify failure modes.