Critical Role of Pits in Suppressing Li Dendrites Revealed by Continuum Mechanics Simulation and In Situ Experiment

Abstract

Dendrite growth and surface pitting are critical factors hindering the development of ultra-high energy density rechargeable lithium battery. However, the mechanism of dendrite growth promoted by pits on the surface of lithium metal remains unclear. In this study, we propose a combination of continuum mechanics simulations and develop an in situ experimental observation device to investigate the effects of pit size, curvature of pit edge, overpotential, and lithium-ion concentration gradient on dendrite growth. Results show that a larger size and curvature of pits can reduce the deposition rate of lithium and dendrite morphology significantly. Larger overpotential can aggravate dendritic nucleation and thereby promotes dendrite growth. Uneven lithium-ion concentration gradient distribution significantly influences the direction of the dendrite growth and leads to the formation of branches. The lithium deposition behavior near the ideal pit predicted by continuum mechanics is consistent with that observed in the in situ experiments. These results lay the basis for future studies to determine the effect of the surface morphology of lithium metal electrodes on the electrodeposition stability and performance of lithium metal batteries.