Analysis of Battery Materials by STEM

Scanning transmission electron microscopy (STEM) is especially useful for observing the local structures of materials and has recently been employed for evaluating ion-conductive solid electrolytes (SEs) in all-solid-state batteries. However, due to the low electronic conductivity of SEs, the intrinsic structure is often changed by electron beam irradiation. Here, we developed a specialized sample protection technique, termed “nano-shield,” to suppress damage caused by electron beam irradiation. Nano-shield consists of a dual-layer coating combining an amorphous insulating layer of AlOx with an amorphous conductive layer of carbon. The AlOx layer blocks ion diffusion, while the carbon layer prevents charging during electron beam irradiation. By applying nano-shield to samples, we visualized the atomic structures of lithium-ion-conductive SEs, cubic Li7La3Zr2O12 (c-LLZ) and Li1.3Al0.3Ti1.7(PO4)3 (LATP) single crystals at room temperature. Furthermore, we conducted an elemental analysis at atomic resolution, where the impact of electron beam irradiation becomes more critical. The development of this essential technology for high-resolution observation of beam-sensitive SEs presents many opportunities for the elucidation of reaction mechanisms of battery materials.