Tension-Induced Cavitation in Li Metal Stripping.

Designing stable Li metal and supporting solid structures (SSS) is of fundamental importance in rechargeable Li-metal batteries. Yet, the stripping kinetics of Li metal and its mechanical effect on the supporting solids (including solid electrolyte interface) remain mysterious to date. Here, through nanoscale in-situ observations of a solid-state Li-metal battery in an electron microscope, we discover two distinct cavitation-mediated Li stripping modes controlled by the ratio of the SSS thickness (t) to the Li deposit's radius (r). A quantitative criterion is established to understand the damage tolerance of SSS on the Li metal stripping pathways. For mechanically unstable SSS (t/r < 0.21), the stripping proceeds via tension-induced multisite cavitation accompanied by severe SSS buckling and necking, ultimately leading to Li "trapping" or "dead Li" formation; for mechanically stable SSS (t/r > 0.21), the Li metal undergoes nearly planar stripping from the root via single cavitation, showing negligible buckling. Our work, by providing a fundamental understanding of the cycling behavior of Li metal inside supporting solid structures, is of potential importance to the design of delicate Li metal supporting structures to high-performance solid-state Li-metal batteries. This article is protected by copyright. All rights reserved.