Electronmicroscopical
image of Pyrite nanocrystals, which make up the cathode
in the fool’s gold
battery (photo: Empa)
(November 13, 2015) Super
environmentally friendly: the “fool’s gold battery”
High-performance lithium ion batteries face a major problem:
Lithium will eventually start to run out as batteries are deployed in electric
cars and stationary storage units. Researchers from Empa and ETH Zurich have
now discovered an alternative: the “fool’s gold battery”. It consists of iron,
sulfur, sodium and magnesium – all elements that are in plentiful supply. This
means that giant storage batteries could be built on the cheap and used
stationary in buildings or next to power plants, for instance.
There is an urgent need to search for low-priced batteries
to store electricity. Intermittency of green electricity is affecting the power
grids, calling for stationary storage units to be connected into a smart grid.,
Electric cars are of increasing popularity, but are still to explensive.
Efficient lithium ion batteries we know are not suitable for large-scale
stationary storage of electricity; they are just too expensive precious lithium
is too scarce. A cheap alternative is called for – a battery made of
inexpensive ingredients that are available in abundance. But electrochemistry
is a tricky business: Not everything that’s cheap can be used to make a
battery.
The key to
success: pyrite (fool’s gold) as a cathode material.
(photo: JJ
Harrison/commons.wikimedia.org)
Safe, durable and
affordable
Maksym Kovalenko, Marc Walter and their colleagues at Empa’s
Laboratory for Thin Films and Photovoltaics have now managed to pull off the
unthinkable: by combining a magnesium anode with an electrolyte made of
magnesium and sodium ions. Nanocrystals made of pyrite – more commonly known as
fool’s gold – serve as the cathode. Pyrite is crystalline iron sulfide. The
sodium ions from the electrolyte migrate to the cathode during discharging.
When the battery is recharged, the pyrite re-releases the sodium ions. This
so-called sodium-magnesium hybrid battery already works in the lab and has
several advantages: The magnesium as the anode is far safer than highly
flammable lithium. And the test battery in the lab already withstood 40
charging and discharging cycles without compromising its performance, calling
for further optimization.
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