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 chassis 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. In addition, they are scalable to large volumes, unlike other batteries such as lithium-ion. All this offers a sustainable and clean system that can help reduce dependence on fossil fuels. The first vanadium redox (reduction-oxidation) batteries began to be developed in the late 1980s thanks to the pioneering work of Greek-Australian chemical engineer Maria Skyllas-Kazacos, and have been used commercially for the last decade.
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. There are also certain technical limitations that affect the performance of these batteries, such as vanadium precipitation at high temperatures or the deterioration of the materials. Attempts are currently being made to overcome these limitations by improving the composition of the electrolytes and testing new, more efficient materials for the membrane, electrodes and other components.
Another drawback is price, though this is not due to the metal’s scarcity as it’s the 22nd most abundant element in the earth’s crust, 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 the world’s vanadium production is used for the steel industry, leaving little supply available for other uses. The main producers are South Africa, Russia and China, the latter also being the world’s largest consumer, even more so following a recent change in earthquake construction regulations. With China also reducing its vanadium production as part of its new policies against emissions and environmental pollution, the result is that this metal has been subject to a supply crunch that has pushed up its prices. However, although up to now only 2% of world production has been used for storage batteries, expert forecasts estimate that by 2027 these batteries could account for 18% of the energy storage market and that by 2050 the demand for vanadium in this sector could double the entire global production of 2018.
In fact, the nature of vanadium as a by-product of mining means that 70% of the vanadium that is extracted remains unused. But given the difficulty of exploiting it, research is also being done into production from other alternative sources to break the dependence on mining. Rehder mentions seawater, 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 a metal, vanadium, in which many experts see the future of energy storage.