Augment your battery research with non-ambient in-operando XRD – Q&A

First of all, let’s understand the mechanism of X-ray fluorescence. The X-ray fluorescence is manifested by the emission of secondary X-rays from the elements that are excited by incident X-rays. The secondary X-ray photons have lower energy than the incident X-rays photons. In X-ray diffraction, the X-ray fluorescence contributes to an elevated background that appears across the entire 2theta range. To improve the XRD data from the impact of fluorescence, two methods are commonly used. The first method uses a diffracted beam monochromator or high-energy resolution detector (such as 1Der) to separate the fluorescent photon by energy. The second method uses an incident monochromatic beam (such as Bragg-Brentano HD) so that the higher energy photons that can cause fluorescence are removed before irradiating on the sample.  When the battery contains the same element as the X-ray tube anode material such as Co, or Cu. In those cases, the fluorescent photons have identical energy to the characteristic X-rays of the anode material. This makes the monochromator or high energy resolution detector ineffective. The only method is using an incident beam monochromator. The graph below shows the effectiveness of the Bragg-Brentano HD in removing the fluorescence of the Cu element compared to a classic slit optic.  

As shown in the example data, the LiFePO4 crystallite size has a clear dependence on the temperature. The crystallite size is reduced at a lower temperature after going through the same charging-discharging condition at different temperatures.  During the same duration, the crystallite does not grow as fast as at high temperatures due to the reduced electrochemical reaction rate at lower temperatures.  

At the given temperature, the effect of the crystallite on the performance of the battery can be investigated across a series of the battery. We are looking forward to seeing your results studied with VTEC or VTEC-trans. 

In an XRD measurement, the X-ray beam is attenuated by the battery. The intensity should be sufficient to reveal the diffraction peaks of the battery materials within the given data collection duration. To improve the diffraction signal, hard radiation and an efficient detector should be used. Ag or Mo radiation has higher penetration power and the GaliPIX^3D with CdTe sensor detects more effectively the hard X-ray photons with ~ 100% quantum efficiency. Therefore, if the batteries’ dimension and attenuation are compatible with the selected X-rays, it’s possible to investigate them with VTEC-trans. However, the solid-state battery requires a stack pressure load that the VTEC-trans is not designed for.

We have a fully integrated solution with the BioLogic potentiostat. We also have off-the-shelf robust solutions for potentiostat brands such as Maccor, Ivium, Lanhe. But any potentiostat can be used with VTEC or VTEC-trans stages when the integrated control is not a must. If you are interested in an integrated solution with a specific type of potentiostat, please reach out to us for a customized solution.