The formation of lithium dendrites at the anode during charging can result in capacity fade and potentially lead to internal short circuits. Adopting high capacity next-generation technologies, such as Li-air or Li-S, exacerbates this problem. Although this phenomenon has been known to be a primary safety concern and source of failure for decades, limited remedies exist to suppress dendrites growth. This partially stems from our limited understanding of the mechanism(s) governing Li dendrite nucleation and growth during cycling. While several models have been proposed, a general agreement has yet to be reached, which motivates our current work.

In this work, in-situ scanning electron microscopy was used to investigate the growth of lithium dendrites. The cell was composed of lithium cobalt oxide as the cathode, carbon film as the anode, and a Li imide salt dissolved in P₁₃TFSI ionic liquid as the electrolyte. We were able to observe operando growth of lithium dendrites on the carbon film. The experimental configuration differs from typical Li-ion systems, since the dendrites do not grow along the field gradient, suggesting that this is not the primary source of dendrite growth. The morphologies and growth rates of lithium dendrites were characterized as a function of time and applied voltage. Additionally, the focused ion beam was utilized to cross section the lithium dendrites in-situ in order to characterize the internal morphology. The results provide new insights into the roles of surficial reactions and stresses in driving the formation of dendrites.