Quantum Dots Made from Fool's Gold Boost Battery Performance

Estimated reading time: 4 minutes

According to Pint, “You can think of it like vanilla cake. Storing lithium or sodium in conventional battery materials is like pushing chocolate chips into the cake and then pulling the intact chips back out. With the interesting materials we’re studying, you put chocolate chips into vanilla cake and it changes into a chocolate cake with vanilla chips.”

As a result, the rules that forbid the use of ultrasmall nanoparticles in batteries no longer apply. In fact, the scales are tipped in favor of very small nanoparticles.

“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.

A transmission electron microscope image of a single iron pyrite quantum dot on the left and a graph that shows the size distribution of the fool's gold quantum dots that they added to standard lithium batteries. (Pint Lab / Vanderbilt)

Pint believes that understanding of chemical storage mechanisms and how they depend on nanoscale dimensions is critical to enable the evolution of battery performance at a pace that stands up to Moore’s law and can support the transition to electric vehicles.

“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.”

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