Regulating the solvation sheath of Li ions by using hydrogen bonds for highly stable lithium-metal anodes

The performance of Li anodes is extremely affected by the solvation of Li ions, leading to preferential reduction of the solvation sheath and subsequent formation of fragile solid-electrolyte interphase (SEI), Li dendrites, and low coulombic efficiency (CE). Herein, we propose a novel strategy to regulate the solvation sheath, through the introduction of intermolecular hydrogen bonds with both the anions of Li salt and the solvent by small amount additives. The addition of such hydrogen bonds reduced the LUMO energy level of anions in electrolyte, promoted the formation of a robust SEI, reduced the amount of free solvent molecules, and enhanced stability of electrolytes. Based on this strategy, flat and dense lithium deposition was obtained. Even under lean electrolytes, at a current density of 1 mA cm${}^{-2}$ with a fixed capacity of 3 mAh cm${}^{-2}$, the Li-Cu cells showed an impressive CE value of 99.2 %. The Li-LiFePO${}_4$ full cells showed long-term cycling stability for more than 1000 cycles at 1 C, with a total capacity loss of only 15 mAh g${}^{-1}$. (© 2021 Wiley-VCH GmbH)