Abstract: Lithium (Li) metal anodes promise an ultrahigh theoretical energy density and low redox potential, thus being the critical energy material for next-generation batteries. Unfortunately, the formation of Li dendrites in Li metal anodes remarkably hinders the practical applications of Li metal anodes. Herein, the dynamic evolution of discrete Li dendrites and aggregated Li dendrites with increasing current densities is visualized by in-situ optical microscopy in conjunction with ex-situ scanning electron microscopy. As revealed by the phase field simulations, the formation of aggregated Li dendrites under high current density is attributed to the locally concentrated electric field rather than the depletion of Li ions. More specifically, the locally concentrated electric field stems from the spatial inhomogeneity on the Li metal surface and will be further enhanced with increasing current densities. Adjusting the above two factors with the help of the constructed phase field model is able to regulate the electrodeposited morphology from aggregated Li dendrites to discrete Li dendrites, and ultimately columnar Li morphology. The methodology and mechanistic understanding established herein give a significant step toward the practical applications of Li metal anodes.

Key words: Electrochemistry, Li dendrites, Rechargeable Li batteries, In-situ optical microscopy, Phase field model, Electrochemical engineering

摘要： Lithium (Li) metal anodes promise an ultrahigh theoretical energy density and low redox potential, thus being the critical energy material for next-generation batteries. Unfortunately, the formation of Li dendrites in Li metal anodes remarkably hinders the practical applications of Li metal anodes. Herein, the dynamic evolution of discrete Li dendrites and aggregated Li dendrites with increasing current densities is visualized by in-situ optical microscopy in conjunction with ex-situ scanning electron microscopy. As revealed by the phase field simulations, the formation of aggregated Li dendrites under high current density is attributed to the locally concentrated electric field rather than the depletion of Li ions. More specifically, the locally concentrated electric field stems from the spatial inhomogeneity on the Li metal surface and will be further enhanced with increasing current densities. Adjusting the above two factors with the help of the constructed phase field model is able to regulate the electrodeposited morphology from aggregated Li dendrites to discrete Li dendrites, and ultimately columnar Li morphology. The methodology and mechanistic understanding established herein give a significant step toward the practical applications of Li metal anodes.

关键词: Electrochemistry, Li dendrites, Rechargeable Li batteries, In-situ optical microscopy, Phase field model, Electrochemical engineering