Episode 56 | Alkaline Advantage | Naval Research Laboratory
For my fourth and final interview at the Naval Research Laboratory, I was introduced to Dr. Debra Rolison, senior scientist and principal investigator on the "Zinc Sponge" technology, a solution for making alkaline batteries rechargeable.
As a kid, I never understood why cheaper alkaline batteries could not go in the battery charger for my remote-controlled car. Turns out they can, but 1) it'll form hydrogen gas, and 2) spiky dendrites form and will eventually puncture through the membranes.
In 2017, Rolison and her team published their work on the Zinc Sponge designs. They start by creating an emulsion, similar to Italian salad dressing, made up of water, oil, an emulsifier (carboxymethyl cellulose) and zinc powder.
This emulsion keeps the zinc more uniformly reactive. Yes, it will form a "carpet of baby spikes," as Rolison puts it, but not enough to ever form dendrites.
For the publication's study, funded by ARPA-E and industry partner EnZinc, the team shrunk the sponge down to 500 microns, thin enough to cycle 100 times. The goal of the study was to show that the cell could be put through the paces similar to a lithium ion (Li-ion) battery, or about 40% zinc oxidation every cycle.
Rolison says her batteries could be competitive with Li-ion batteries on a few levels:
- Zinc is 4x more abundant on earth than lithium, and more evenly distributed (Zn vs. Li-ion)
- Though Li-ion batteries have a higher voltage, Zn batteries would not need as much heavy "catastrophe management," which can make up a large portion of the weight of the system
- Zn batteries would not as much quality control as Li-ion during manufacturing
She says EnZinc partnered up with them in the hopes of eventually developing a Nickel-Zinc system for electric vehicles. Rolison also hopes the traditional alkaline battery manufacturers we're familiar with will want to license the technology as well, because they have the knowhow to manufacture on a large scale.
This being the Navy, Rolison says their next step is to develop a 2.5-amp hour pouch cell to test with the military. They also brought in a postdoc with a Ph. D. in mechanical engineering from MIT to develop more robust cells.
They have also patented and are developing a 2nd-generation zinc sponge. This one, she says, uses varied zinc power sizes as well as pairing them with silver to "get unprecedented rechargeability and continuous power that starts to tickle the bottom of electrochemical capacitors,” which most lithium ions don’t do.
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