Progressive and instantaneous nature of lithium nucleation discovered by dynamic and operando imaging

Abstract

The understanding of lithium (Li) nucleation and growth is important to design better electrodes for high-performance batteries. However, the study of Li nucleation process is still limited because of the lack of imaging tools that can provide information of the entire dynamic process. We developed and used an operando reflection interference microscope (RIM) that enables real-time imaging and tracking the Li nucleation dynamics at a single nanoparticle level. This dynamic and operando imaging platform provides us with critical capabilities to continuously monitor and study the Li nucleation process. We find that the formation of initial Li nuclei is not at the exact same time point, and Li nucleation process shows the properties of both progressive and instantaneous nucleation. In addition, the RIM allows us to track the individual Li nucleus’s growth and extract spatially resolved overpotential map. The nonuniform overpotential map indicates that the localized electrochemical environments substantially influence the Li nucleation.

A Deeper Understanding of Metal Nucleation and Growth in Rechargeable Metal Batteries Through Theory and Experiment

“…[35,[39][40] In a recent work by Feng, et al the nucleation of Li on Cu (mimicking a Li anode-free battery) was observed in situ using a reflection interference microscope (RIM). [41] They identified a transition in nucleation mode from progressive to instantaneous as the SEI was formed. Initially, SEI formation reactions decreased Li nucleation rate, inducing progressive nucleation.…”

“…This was attributed to the structure of the SEI on these areas, but the morphology of the Li, and therefore Li flux would also play a significant role. [41] The method developed by Feng, et al may be valuable for observing in situ nucleation and stripping of a range of metals and should be applied to other systems to confirm if the nucleation mode switching behaviour observed is common. Nucleation mechanisms can clearly impact the morphology of an electrodeposited metal and therefore dendrite formation.…”

“…The areas where Li had most recently deposited were stripped first before areas which had “older” deposits. This was attributed to the structure of the SEI on these areas, but the morphology of the Li, and therefore Li flux would also play a significant role [41] . The method developed by Feng, et al.…”

Kelvin Probe Force Microscopy and Electrochemical Atomic Force Microscopy Investigations of Lithium Nucleation and Growth: Influence of the Electrode Surface Potential

“…This voltage stabilization is a characteristic of the formation of an ion-conductive SEI layer at the electrified interface. 29 , 30 However, differences were evident in the nucleation overpotentials for the three systems. The Au/Cu system demonstrated the highest nucleation overpotential at −0.7865 V Li/Li + , suggesting a higher energy barrier for Li nucleation than the other systems.…”