Understanding the solid electrolyte interphases in battery systems by electrochemical atomic force microscopy and its derivatives

Gaining fundamental insights of the interfacial electrochemistry in advanced battery systems, specifically the solid electrolyte interphases (SEIs), are key for the development of their practical applications. Electrochemical atomic force microscopy (EC-AFM) and its derivatives have been regarded as powerful and promising tools to reveal the SEI formation and evolution at the micro-/nanoscale and in real time. In this review, we present EC-AFM observations of the dynamic processes and structures of SEI in both liquid and solid electrolyte batteries. We show functional modes that enable the high-resolution monitoring of local modulus, viscosity, and ionic migration. Related techniques, mainly scanning electrochemical microscopy, are also introduced for probing the electrochemical reactivity and its distribution.