Probing the Mechanically Stable Solid Electrolyte Interphase and the Implications in Design Strategies

The inevitable volume expansion of secondary battery anodes during cycling imposes forces on the solid electrolyte interphase (SEI). The battery performance is closely related to the capability of SEI to maintain intact under the cyclic loading conditions, which basically boils down to the mechanical properties of SEI. The volatile and complex nature of SEI as well as its nanoscale thickness and environmental sensitivity make the interpretation of its mechanical behavior many roadblocks. Widely varied approaches are adopted to investigate the mechanical properties of SEI, and diverse opinions are generated. The lack of consensus at both technical and theoretical levels has hindered the development of effective design strategies to maximize the mechanical stability of SEIs. Here, the essential and desirable mechanical properties of SEI, the available mechanical characterization methods, and important issues meriting attention for higher test accuracy are outlined. Previous attempts to optimize battery performance by tuning SEI mechanical properties are also scrutinized, inconsistencies in these efforts are elucidated, and the underlying causes are explored. Finally, a set of research protocols is proposed to accelerate the achievement of superior battery cycling performance by improving the mechanical stability of SEI.

Automated summary

The volume expansion of secondary battery anodes during cycling affects the solid electrolyte interphase (SEI). SEI's mechanical properties play a crucial role in maintaining battery performance under cyclic loading conditions. However, due to SEI's volatile and complex nature, interpreting its mechanical behavior faces challenges. Different approaches have been used to study the mechanical properties of SEI, leading to varied opinions and hindering the development of effective design strategies. This article outlines the essential mechanical properties of SEI, available characterization methods, and issues that need attention for improved test accuracy. It also examines previous attempts to optimize battery performance by tuning SEI mechanical properties, identifies inconsistencies, explores underlying causes, and proposes research protocols to enhance battery cycling performance by improving SEI's mechanical stability.