MIT researchers have just discovered an alloy that, if used as a catalyst, makes lithium-air batteries more efficient. This type of battery works by reacting the metal lithium with the oxygen from the air, and is very efficient at storing high amounts of energy (three times more than lithium ion). The industry awaits the development of lithium air batteries so they can be used in future electric cars.
The catalyst that the MIT scientists, led by Yang Shao-Horn, have produced is made of nanoparticles of a gold and platinum alloy. Both platinum and gold are unresponsive as catalysts when the battery discharges. The scientists had studied them earlier, but only now have they understood that a mix of the two is making a difference in the way that the battery charges. When that happens, oxygen is released from the battery and lithium metal reforms.
The lithium air batteries developed so far as prototypes, despite their charging capacity, have some important issues, such as very limited charge/discharge cycles, they release their energy slowly and are very sensitive to carbon dioxide and water, which could contaminate them easily. One very important characteristic of a battery is its lifetime, and the discovery of this new catalyst addresses it directly.
Testing the battery equipped with the fore-mentioned catalyst, the MIT researchers were able to obtain a 77 percent efficiency, meaning that they got back 77% of the energy they put into that battery. The earlier record was 70 percent. It is expected that the final commercially-available lithium air batteries to reach efficiencies of 85 to 90 percent.
Actually, the fact that gold is a poor catalyst for the battery when it discharges had been discovered and patented by Toyota before Shao’s team figured it.
Not wanting to make the batteries more expensive by adding gold and platinum (two expensive metals), the team is now studying ways to coat nanoparticles of a cheaper material with the alloy of the two expensive ones. A French researcher, Jean-Marie Tarascon, a professor at the Universite de Picardie Jules Verne, has discovered recently that manganese oxide is even more efficient than Shao’s bi-metal catalyst. But there are a many parameters that need to be discussed about this first, and we’ll see whose idea wins, eventually.
