In situ/operando methods for investigation of ionic transport mechanisms in solid-state architectures

Solid-state electrolytes (SSEs) hold great promise of overcoming the inherent limits of liquid electrolytes for lithium-ion batteries (LIBs) applications because of their inherent advantages over the liquid electrolytes. Substantial efforts have been taken to improve energy density, cycle life, and safety of LIBs by combining liquid electrolytes with SSEs or replacing liquid electrolytes with SSEs. However, the employment of SSEs in commercial LIBs has been impeded by the limits of current SSEs such as low ionic conductivity, instability, poor interfacial stability, high interfacial resistance, and so on. To overcome these limits, fundamental understanding of ionic transport through multiphase interfaces is needed, which requires advanced in situ/operando characterization techniques to probe the buried SSEs, interface and interphases, and intra-electrolyte interfaces. Therefore, in situ/operando characterization on the SSEs has attracted more research attention in the past few decades, and significant progress has been made. This chapter briefly summarizes the recent progress on the in situ/operando characterization on the SSEs with a variety of advanced microscopic and spectroscopic techniques with innovative experimental settings, as well as the new fundamental insights achieved by these experimental characterization advancements.