It was said that if a hair fell on a sword made of Damascus steel, it would split cleanly in two. Now we know that the secret of the powerful Arabian scimitars that inspired terror in Christian crusaders was vanadium, a then unknown element that was extracted along with iron, and is currently used by industry to increase the strength of steel. But beyond that historical use, the still little known vanadium expects to see a boom in popularity in the coming years. The renewable energy sector has recently taken an interest in this metal thanks to its unique chemical properties that permit the manufacture of more efficient batteries to store energy from solar and wind power installations.
The first discoverer of vanadium was the Spaniard Andrés Manuel del Río, a figure little known in his own country, who rubbed shoulders with the likes of the German naturalist Alexander Von Humboldt and the French chemist Antoine Lavoisier, of whom he was a student. With the arrival of the French Revolution, it is said that del Río fled disguised as a water seller, in this way avoiding sharing the same fate as his aristocratic mentor, who was executed by the guillotine. Having emigrated to Mexico, in 1801 he discovered a mineral he called “brown lead” suspected of containing a new element, which he named erythronium. The sample was delivered to Von Humboldt and analyzed in Europe: the conclusion was that it contained the already-known chromium, but no new element.
In April 1830, the Swedish chemist Nils Gabriel Sefstrom rediscovered vanadium. He found it in an iron ore and did manage to demonstrate that it was a new metal. After considering names such as odinium and erian, he finally decided to name it in honor of the Norse goddess Vanadis, a symbol of beauty and fertility.
The secret of the Arab swords was soon attributed to vanadium when it was found that adding it to steel in small amounts would produce stronger alloys. The magnate Henry Ford used it in the body of his famous Model T, the automobile that put the American middle class behind the wheel. During the 20th century, the use of vanadium was extended to applications that needed particularly strong and resilient steel alloys, such as certain tools, industrial machinery and building structures.
More stable and longer-lasting batteries
The great peculiarity of vanadium is that it exhibits four different oxidation states in solution, which is quite unusual. According to the explanation given to OpenMind by expert Dieter Rehder, chemist and professor at the University of Hamburg (Germany), “in the process of charging and discharging, vanadium can store and release four electrons per atom. This makes vanadium compounds particularly efficient storage materials for batteries.”
So-called “flow batteries” store electrical energy in chemical form thanks to the exchange of ions through a membrane separating two solutions of compounds at different oxidation levels. The advantage of vanadium is that its four oxidation states allow for the manufacture of batteries that are stable and long-lasting — qualities which are especially useful when the power source is not constant, such as with solar and wind power. Wind is naturally variable and solar energy is only produced during the day, precisely when certain uses of electricity, such as lighting, are not needed. Vanadium flow batteries can store electrochemical energy for hours and then release it later at a controlled rate according to demand.
Technological constraints and environmental concerns
However, every technology has its limitations and for vanadium flow batteries the first one is size. Since the batteries are as big as trucks, they are not an option for portable uses. Another drawback is price, though this is not due to the metal’s scarcity as it’s the 22nd most abundant element in the periodic table, ahead of copper and zinc. The problem is that “the majority is scattered through the earth’s crust and oceans, and enrichment from these sources is not an easy task,” says Rehder, author of Bioinorganic Vanadium Chemistry (Wiley, 2008). Although the extraction of this mineral is not complicated, it is still polluting. “Mining and processing of vanadium can be accompanied by relatively high discharges of vanadium pentoxide V2O5, which is somewhat toxic by inhalation,” says Rehder. “High concentrations of vanadium can also be dangerous for animals and plants.”
Some 90% of world production is used to make vanadium steel alloys and as a catalyst, for example in the manufacture of sulfuric acid. China, the main producer, also absorbs most of its output to supply its own construction boom, leaving little available for other uses. For this reason, the battery manufacturer Imergy resorts to recycling fly ash and iron ore slag from steel manufacturing.
Rehder mentions seawater as a possible alternative source, but there is another, perhaps more useful, resource. “Some marine inhabitants, particularly ascidians, are able to gather vanadium from water by a factor of up to ten million,” he says. Something similar happens on land with the hallucinogenic mushroom Amanita muscaria. One possibility would be to learn how to copy industrially what these organisms do in the wild with vanadium. In any case, regardless of how it’s produced, this metal promises to be increasingly prized.