TEM of hydrated and dehydrated birnessite

I had a reason to look at Matt Kim’s PhD dissertation, which was about synthesis of layered MnO2 birnessite compounds for Li-ion and Na-ion batteries. We published his work in this paper, but at the end of his dissertation I saw this image that didn’t make it into the paper. On the left you see a regular birnessite with a 7 angstrom interlayer, and on the right you see a dehydrated version, which is smaller because it is dehydrated and the interlayer H2O is gone.

I was looking at this and I was amazed because on the left I can see the H2O molecules between the layers. On the right you see black space only. Kind of a work of art. Matt, I’m sorry I left this out of the paper. Cutting the 60 figures down into a manuscript wasn’t the most orderly process, and I really should have left this one in. 🙂

Modeling High Current Pulsed Discharge in AA Battery Cathodes: The Effect of Localized Charging during Rest

New paper from us at ACS Applied Energy Materials (open access). We modeled the localized charging and discharging (i.e. balancing) that happens in a battery after a high current pulse. Great work by Dominick Guida in collaboration with Energizer.

I *wanted* this paper to be about adapting Marcus-type kinetics to MnO2 electrochemistry. But no matter what we tried, adapting a Butler-Volmer expression fit the data better. (AMH=asymmetric Marcus–Hush kinetics.)