Liquid Metal Batteries

There has been at least one exciting development in batteries
in recent years. A convenient name is liquid metal batteries.
They offer low manufacturing costs, extreme power density,
and suitability for grid-scale storage.

Sodium-sulfur batteries were known in the 1980's, as a well-
publicized research effort by Ford Motor Company. Those
devices differ from the new liquid metal batteries, particularly
in the form of the separator (electrolyte) between the
electroactive materials. They are closely related.

One of the key advantages of batteries with liquid electroactive
materials is that there are no morphology changes on cycling,
such that the cycle life of the active materials may approach
infinite. In the sodium-sulfur cells, this condition is met for
the anode and cathode materials (being molten sodium and
molten sulfur, respectively), but the solid electrolyte (a beta-
aluminum oxide ceramic ion conductor) is susceptible to
mechanical degradation by the phase change occurring as the
sodium ions are reduced to the metallic state, as well as by
the corrosive effects of liquid sodium.

In the new liquid metal batteries, molten salt serves as both
the separator and electrolyte. Density differences allow two of
the three liquid layers to float on the heaviest layer. In some
sense, the battery is self-assembling. The very high ionic
conductivity of the electrolyte allows for extreme power
density, well suited to grid-scale power storage. The safety
issues implicit in molten materials make them not particularly
attractive for use in electric vehicles, but in time may be
resolved. In the proof-of-concept cell by Donald Sadoway's
research group at MIT, the three layers, from bottom to top,
are antimony, sodium sulfide and magnesium. During
discharge, the top and bottom layers are consumed to form
magnesium antimonide, which dissolves in the electrolyte.
Upon recharge, the metal layers are reformed. If corrosion
issues for the electrodes and container can be resolved, the
cycle life may be nearly infinite.

I was pleased to receive from Mark Mack, a consultant to the
chemical industry, www.markmackllc.com, the article linked
below. It discusses state-of-the-art battery technology and
research and it reminded me about the important innovation in
battery technology represented by the liquid metal cells, so
directly led to this article. Dr. Mack, his coathor, Dr. Pitchai,
and Batteries International have kindly given permission to
distribute their article as part of the Techbriefing series.
The article can be found here:

http://sites.google.com/site/matbriefing/home/filecabinet/Batteries2010.pdf

Mark Mack is organizing a marvelous conference styled
Charged2020 http://www.charged2020.com/ to be held in San
Diego 30 June to 02 July 2010 to address energy storage
challenges. The importance of energy to the global economy
cannot be overstated.

Donald Sadoway of MIT discusses his invention of one liquid
metal battery:

http://www.buildbabybuild.com/news/prof-donald-sadoway-talks-about-liquid-battery-technology-review

An earlier article on innovations in battery technology can be
found here:

http://sites.google.com/site/matbriefing/home/filecabinet/SCAMPER2010.pdf

Another type of electrical energy storage device that employs
liquid electroactive materials has been called a flow battery,
a redox battery and redox regenerative fuel cell. Those devices
will be the subject of a future Techbriefing post.

Full disclosure: I have owned US Antimony (UAMY) stock for the past
5 years and this article made me think that it might be a good
idea to buy more. So I did. This is not investment advice. I
am not an investment adviser. Do not confuse this free article
with a recommendation to buy or sell any stock or other
financial vehicle.