In a study published in journal Nature Communications, scientists have published a new technique using which they are able to pinpoint nanoscale chemical reactions inside batteries.
The ability to pinpoint these chemical reactions inside lithium-ion batteries will enable scientists to identify how a battery operates and uncover how the battery might be optimized to make it work even better. This technique will help scientists understand at nano-scale the charging and discharging of batteries and the effect of these events on the components of the batteries.
Tools available to study these reactions can only provide information on the average composition of electrodes at any given point in time giving researchers the information about what percentage of the electrode has become permanently oxidized. But these tools cannot provide information on the location of oxidized portions in the electrode. Because of these limitations, it is not possible to tell if reactions are confined to a certain area of the electrode, such as the surface of the material, or if reactions are taking place uniformly throughout the electrode.
The new technique, called X-ray ptychographic tomography, came about through a partnership between chemists at UIC and scientists at the Advanced Light Source, at Lawrence Berkeley National Laboratory in California. Advanced Light Source scientists developed the instrumentation and measurement algorithms, which were used to help answer fundamental questions about battery materials and behavior identified by the UIC team.
Together, the two teams used the tomographic technique to look at tens of nanoparticles of lithium-iron phosphate recovered from a battery electrode that had been partially charged. The researchers used a coherent, nanoscale beam of X-rays generated by the high-flux synchrotron accelerator at the Advanced Light Source to interrogate each nanoparticle. The pattern of absorption of the beam by the material gave the researchers information about the oxidation state of iron in the nanoparticles in the X-ray beam. Because they were able to move the beam just a few nanometers over and run their interrogation again, the team could reconstruct chemical maps of the nanoparticles with a resolution of about 11 nanometers. By rotating the material in space, they could create a three-dimensional tomographic reconstruction of the oxidation states of each nanoparticle. In other words, they could tell the extent to which an individual nanoparticle of lithium iron phosphate had reacted.