Dendrite Growth Suppression and in-Situ Surface Observation of Lithium Battery Under an Optical Microscope

Dendrite growth is a major obstacle to the commercialization of lithium metal batteries. A dendrite formed on a Li anode can cause thermal run-aways and permanent capacity loss. Despite previous research efforts, the behavior of lithium dendrite growth is elusive since it is related to multiple factors. An i n-situ optical techniques is considered as one of the major methods to study the dendrites growth behaviors and morphologies real-time. A better knowledge of the physico-chemical processes and the side reactions during a battery operation can be gained. A home-designed in-situ optical cell with a digital optical microscope was used to investigate the behavior of Li deposition on a metallic Li electrode under different electrochemical operation conditions. The impacts of electrolytes, additives and cycling conditions on the dendrite formation were investigated. The changes of the morphology and the shape of the dendrites were investigated correspondingly. Guiding by the in-situ optical observation results, polycyclic aromatic hydrocarbons (PAHs) were introduced as additives to suppress the dendrite growth. It was observed in an in-situ optical experiment, that the freshly formed dendrites can be dissolved and dispersed throughout the surface, eventually a dynamic elastic protection layer was formed. With the liquid electrolyte trapped in the protection layer, the thickness of the layer could be self-adjusted to compensate for the volume change of the Li anode during the battery cycling. Among the eight additives added to the electrolyte, several PAH additives have significant effect on suppressing dendrite growth and greatly enhance the cyclability of the Lithium electrode in a symmetry Li/Li cell. Tarascon, J.-M., & Armand, M. (2001). Issues and challenges facing rechargeable lithium batteries. Nature, 414(6861), 359–367. Tripathi, A. M., Su, W.-N., & Hwang, B. J. (2018). In situ analytical techniques for battery interface analysis. Chemical Society Reviews, 47(3), 736–851. Figure 1