The poor performance and safety concerns of Li metal anodes represents a critical challenge to enable high energy density rechargeable batteries. This is attributed to the evolution of Li metal morphology during cycling, which leads to dendrite growth and surface pitting. Herein, we present a comprehensive understanding of the voltage variations observed during Li metal cycling, which is directly correlated to morphology evolution through the use of operando video microscopy. A custom-designed visualization cell was developed to enable in situ synchronized observation of Li metal electrode morphology and electrochemical behavior during cycling. A mechanistic understanding of the complex behavior of these electrodes is gained through correlation with continuum-scale modeling, which provides insight into the dominant surface kinetics. This work provides a comprehensive explanation of (1) when dendrite nucleation occurs, (2) how those dendrites evolve as a function of time, (3) when surface pitting occurs, (4) kinetic parameters that dictate overpotential as the electrode morphology evolves, and (5) how this understanding can be applied to evaluate performance in a variety of electrolytes. An understanding of how the impedance of reaction pathways change during cycling is used to provide predictive insight into the behavior of Li metal anodes (Fig. 1). This provide detailed insight into the interplay between morphology and the dominant electrochemical processes occurring on the Li electrode surface through an improved understanding of changes in cell voltage, which is a powerful new platform for analysis.

Dendrites and pits: Untangling the complex behavior of lithium metal anodes through operando video microscopy

253rd National Meeting (2017)

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