Here's a recipe for basic chemistry: Mix a bunch of stuff in a reaction vessel and see what happens. Only you don't really see the action taking place -- unless you have some way to visualize the molecular magic.
Researchers at Brookhaven National Laboratory have developed just such a technique: They've fabricated a transparent chemical reactor vessel that allows x-rays to pass through and capture the chemical changes as they take place.
They recently used this real-time reaction monitoring setup to study the synthesis of lithium iron phosphate and pinpoint the best conditions for producing a defect-free material for rechargeable batteries.
Jason Graetz, a materials scientist and leader of Brookhaven's energy storage group, explains the benefits this way:
Generally we make battery materials in a stainless steel reactor. There's no window, no way to see the reaction -- we just see what goes in and what comes out. So we designed a reactor made out of a glass capillary and, using synchrotron x-ray diffraction, we can not only probe the precursors -- the initial parts of the reaction -- but we can also track what happens as the reaction takes place.
The scientists started with a slurry of both solid and liquid precursors, placed them in the glass capillary reaction vessel, and placed the whole setup in beamline X14A at the National Synchrotron Light Source (NSLS), a source of extremely bright x-rays and other forms of light for probing materials' structure and properties. As the x-rays pass through the transparent reaction vessel, they bounce off, or get diffracted by, the atoms in the reactor, producing a pattern that reveals the atomic structure of the various materials in the reactor and how they change as the reaction takes place.
Because we're getting the diffraction pattern, we can learn something about the structure. By analyzing these diffraction patterns, we can also learn about the defect concentration in the material and can track the defects in real time as a function of temperature or time in the reaction.
By doing a series of experiments at different temperatures and different lengths of time, the scientists can identify where the defects are and where they start to disappear, allowing them to pinpoint the lowest temperature and the simplest reaction to produce a defect-free material. This research should therefore eliminate the need for further processing, thus reducing the cost of the most expensive part of lithium-ion batteries.
Read more about the work here.
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