Molten Air Batteries

Reed Miller
December 14, 2014

Submitted as coursework for PH240, Stanford University, Fall 2014

How Batteries Work

Fig. 1: A typical battery. (Source: Wikimedia Commons)
Fig. 2: Molten carbonate fuel cell. (Source: Wikimedia Commons)

At a simple level, batteries are made up of three separate parts: The anode, cathode, and some form of electrolyte. When a battery is connected to an electric circuit, a chemical reaction takes place in the electrolyte causing ions to flow through it one way, and electrons to flow through the outer circuit in the other direction. (An example of a simple battery can be seen in Fig. 1). This movement makes an electric current flow through the cell and through the circuit it is connected to.

What Makes These Batteries Different

"A variety of metal/molten sulfur batteries have been presented. The light weight of sulfur makes these systems attractive for electrochemical energy storage." [1] While said batteries are old news and use molten sulfur, batteries that use other molten elements are in development. (One of these is shown in Fig. 2). These batteries could have a major impact on energy and transportation. These new batteries are lighter than traditional batteries. This is possible because the new batteries use oxygen from the air as the cathode material instead of an internal oxidizer. Additionally these batteries utilize an abnormally high capacity for electrons. The researchers responsible for making the new batteries started with iron, carbon or vanadium boride for their ability to transfer multiple electrons. The primary researcher, Stuart Licht, discusses a similar process in what he calls "super-iron batteries": "This larger apatite for electrons translates directly to increased storage capacity [...] with super-iron cathodes that have up to 47% greater than standard manganese dioxide batteries of the same size." [2] While other multiple-electron-per-molecule batteries may have high storage capacities, they are usually not rechargeable. But, these new batteries offer both features. There is skepticism for the battery's use in a vehicle, being that the battery runs at 700-800 degrees Fahrenheit, but these temperatures are reached in traditional combustion engines. Additionally, the high levels of heat actually play to batteries' own advantages. "Provided however, that the application is one which requires a stored energy greater than 10kWh, hot batteries have attractive characteristics [...] their performance is independent of the ambient temperature". "This requirement to keep the batteries hot means that applications are limited to those in which the size of the battery is substantial (to minimize heat loss) and where the battery is used intensively." [3] The perfect application for such a hot, oxygen powered battery: an electric car battery.

© Reed Miller. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] S. Licht and D. Peramunage, "Novel Aqueous Aluminum/Sulfur Batteries," J. Electrochem. Soc. 140, L4 (1993).

[2] A. Hellemans, "'Super-Iron' Comes to the Rescue of Batteries," Science 285, 995 (1999).

[3] J. L. Sudworth, "High-Temperature Battery Systems," Phil Trans. R. Soc. A 354, 1595 (1996).