The special issue of Microscopy on challenges for lithium detection

摘要

Light elements such as lithium and hydrogen are very important, not only in physics or chemistry but also in biology. Recently, the lithium ion battery (LIB) or fuel cell has been extensively studied: the movement of lithium ions or protons is a significant factor in the performance. The detection of light elements has been expected for a long time, but it has been very difficult because of the small atomic radius and also the small interaction with incident X-ray and electron beam. Concerning the former, it is necessary to improve the spatial resolution to below 0.15 nm for lithium and below 0.05 nm for hydrogen. In this sense, the recent development of the spherical aberration corrector is a turning point, since the spatial resolution reaches 0.1 nm (depending on the accelerating voltage and the quality of the spherical aberration corrector) by the corrector. Regarding the latter, a statistical approach (multivariable analysis) to a large number of spectrum data obtained at each pixel of the whole image by energy loss spectroscopy (EELS) or energy-dispersive X-ray has been developed and the small signal from the light elements can be retrieved properly. Over recent years, the detection of light elements has become achievable. Furthermore, based on this technique, the movement of lithium ions can be monitored during the operation of LIB, which is mounted on the TEM holder (operando observation).