This article is basically swiped from Vanderbilt so you can read more there.
If you add quantum dots – nanocrystals 10,000 times smaller than the width of a human hair – to a smartphone battery it will charge in 30 seconds, but the effect only lasts for a few recharge cycles.
However, a group of researchers at Vanderbilt University report in the Nov. 11 issue of the journal ACS Nano that they have found a way to overcome this problem: Making the quantum dots out of iron pyrite, commonly known as fool’s gold, can produce batteries that charge quickly and work for dozens of cycles.
“Instead of just inserting lithium or sodium ions in or out of the nanoparticles, storage in iron pyrite requires the diffusion of iron atoms as well. Unfortunately, iron diffuses slowly, requiring that the size be smaller than the iron diffusion length – something that is only possible with ultrasmall nanoparticles,” Douglas explained.
A key observation of the team’s study was that these ultrasmall nanoparticles are equipped with dimensions that allow the iron to move to the surface while the sodium or lithium reacts with the sulfurs in the iron pyrite. They demonstrated that this isn’t the case for larger particles, where the inability of the iron to move through the iron pyrite materials limits their storage capability.
“The batteries of tomorrow that can charge in seconds and discharge in days will not just use nanotechnology, they will benefit from the development of new tools that will allow us to design nanostructures that can stand up to tens of thousands of cycles and possess energy storage capacities rivaling that of gasoline,” said Pint. “Our research is a major step in this direction.”
There is a lot more at the link than this taster, but basically size matters for battery chemistry. By using some really small nanoparticles the ability of the Iron to migrate to the surface at a reasonable rate is improved. The bulk properties of quite a few materials will change once we get down to agglomerations of a few hundred or thousand atoms, so there is a massive new range of material/chemical properties to explore. There will no doubt also be fortunes to be made by using a clever process to make such small particles with a defined size-range when the improvements in the properties of the final manufactured article are this dramatic.
It should be noted that this is one of those “not there yet” ideas, since they haven’t yet reached the few thousand cycles that we’ll really need for a reasonable rechargeable battery. The wear-out problem is still way too big at the moment. There are however a lot of other materials, sizes and chemistries to play with, so this is more of a heads-up that there are still unexpected things to find in even a well-researched and well-financed subject.