There is a lot of ongoing discussion about the relative merits of different energy sources, and the desirability of moving to more use of renewable resources, such as solar and wind power, and less use of hydrocarbon-based fuels, such as oil and coal. There is also considerable interest in the development of new, more practical electric vehicles, and the infrastructure to support them, in place of cars powered by internal combustion engines. One key problem that affects all of these efforts is that of energy storage in general, and of electrical energy storage in particular. The sun does not shine, and the wind does not blow, all the time; better storage facilities would reduce the need for relatively dirty backup generating facilities. Better batteries could give electric vehicles better performance and longer range.
According to an article in the Technology Review, a group of researchers at MIT has developed a new form of catalyst, using gold and platinum nanoparticles, that significantly improves the efficiency of lithium-air batteries. These batteries have many attractive characteristics: they are much lighter than lithium-ion batteries of comparable capacity, for example, with an energy density potentially three times as great. However, they have been plagued by limited lifetimes and low efficiency. The new catalyst appears to have the potential to address both of these problems:
When lithium-air batteries are discharged, the lithium metal reacts with oxygen to form lithium oxide and release electrons. When charged, oxygen is released and lithium metal reforms. The new catalysts promote these reactions, and so reduce the amount of energy wasted as the cells are charged and discharged. The gold atoms in the catalyst facilitate the combination of lithium and oxygen; the platinum helps the opposite reaction, freeing the oxygen.
Making these reactions more efficient also reduces the accumulation of lithium oxide, which shortens the battery’s useful life.
Research into improvement of the catalyst is continuing: one path is exploring techniques that require smaller amounts of the precious metals; another is examining the use of manganese oxide as an alternative.