Understanding\nthe Self-Healing Electrostatic Shield\nMechanism at the Lithium–Metal Anode Surface

Lithium–metal anodes, with their impressive high\nspecific\ncapacity of approximately 3860 mAh/g, emerge as a promising alternative\nto Li-ion anodes. However, when subjected to higher recharge currents\nfor accelerated battery charging, dendrites tend to form on the Li-metal\nsurface. These dendrites can puncture the separator, leading to short\ncircuits upon contact with the positive electrode. Such short circuits\nin a nonaqueous solvent can trigger runaway reactions, which raises\nsafety concerns. In an effort to limit dendrite formation on the lithium–metal\nanode, the “self-healing” electrostatic shield mechanism\n(SHES) incorporates a small fraction of cesium salts in the electrolyte.\nThese cesium ions remain charged on the surface, migrating toward\nthe dendrites. The migration of Cs-ions to the dendrite surface creates\na charged shield that compels lithium ions to deposit outside the\ndendrites, preventing the dendrite’s undesirable growth. To\ndelve deeper into the working of the SHES mechanism, this study specifically\nutilizes Li and Cs atoms in both solvated and non-solvated configurations.\nThese atoms are employed to be adsorbed onto various sites of the\nLi slab surface. Density functional theory (DFT) calculations are\nemployed to explore the adsorption energy of Cs ions on Li-metal and\ntheir relationship with dendrite formation. In the presence of the\nsolid electrolyte interphase (SEI), Cs ions migrate to damaged areas,\ndepositing over the exposed bare metal surface and grain boundaries.\nWhen the SEI breaks, Cs ions cover the exposed Li surface, creating\na positively charged shield in the exposed area, thereby reducing\nthe pathway for Li plating and subsequent dendrite growth.