Mechanistic understanding of Li dendrites growth by in- situ/operando imaging techniques

Lithium (Li) metal is the holy grail of anode materials for high energy density batteries. However, safety hazards due to the formation of Li dendrites have prevented their commercialization. This study provides a comprehensive review of the recent works on the mechanisms of Li dendrite formation utilizing in-situ and operando imaging techniques. These multiscale and multimodal techniques include optical imaging, electron microscopy, scanning probe microscopy, X-ray imaging, neutron microscopy and resonance-based imaging techniques. Briefly, optical microscopy enables visualization of Li morphological transitions, and if coupled with a Raman spectrometer, can provide chemical imaging of the Li/electrolyte interface. Electron microscopy and scanning probe imaging offer high spatial resolution enabling near-atomic structural studies of Li dendrites and solid electrolyte interphases. X-ray based techniques offer a high beam penetration depth allowing the study of Li microstructure evolution in large cells. Neutron imaging based on 6 Li has higher sensitivity compared to X-ray imaging and can visualize the Li-ion concentration as a function of sample depth, while 7 Li nuclear magnetic resonance allows for quantified analysis of Li microstructures and provide chemical and spatial information on Li microstructural growth. Finally, some prospective directions for further utilization of in-situ/operando imaging techniques in Li anode research was proposed.