How beam damage can skew synchrotron operando studies of batteries

With the advent of high brilliance 4th generation synchrotron sources, the issue of beam damage on the samples cannot be ignored and deserves a wide attention. It is especially true for operando studies in batteries, since the intense photon fluxes are commonly used to probe ever finer effects. Here we report on a quantitative study on the causes and consequences of synchrotron X-ray beam damage in batteries, based on the case study of operando X-ray diffraction. We show that beam damage is caused by the mingled action of dose and dose rate. The after-effects can lie in a broad range, from mild modifications of the crystalline structure to artificial phase transitions, and can thus impede or bias the understanding of the mechanisms at play. From our results, we estimate the doses at which the different effects appear, and provide recommendations for the design of operando synchrotron experiments.