Impact of Lithium-Ion Coordination on Lithium Electrodeposition

Abstract

The lithium dendrite and parasitic reactions are two major challenges for lithium (Li) metal anode—the most promising anode materials for high-energy-density batteries. In this work, both the dendrite and parasitic reactions that occurred between the liquid electrolyte and Li-metal anode could be largely inhibited by regulating the Li+-solvation structure. The saturated Li+-solvation species exist in commonly used LiPF6 liquid electrolyte that needs extra energy to desolvation during Li-electrodeposition. Partial solvation induced high-energy state Li-ions would be more energy favorable during the electron-reduction process, dominating the competition with solvent reduction reactions. The Li-symmetric cells that are cycling at higher temperatures show better performance; the cycled lithium metal anode with metallic lustre and the dendrite-free surface is observed. Theoretical calculation and experimental measurements reveal the existence of high-energy state Li+-solvates species, and their concentration increases with temperature. This study provides insight into the Li+-solvation structure and its electrodeposition characteristics.