Low-Solvent-Coordination Solvation Structure for Lithium-Metal Batteries via Electric Dipole-Dipole Interaction

Abstract

Unveiling inherent interactions among solvents, Li⁺ ions, and anions are crucial in dictating solvation-desolvation kinetics at the electrode/electrolyte interface. Developing an electrolyte with a low ion-transport barrier and minimal solvent coordination in its interfacial solvation structure is essential for forming an anion-derived solid-electrolyte interface, a key component for high-performance Li-metal batteries. In this study, we harness electric dipole-dipole synergistic interactions to formulate an electrolyte with significantly reduced interfacial solvent coordination. Operando characterization and theoretical analysis reveal that 2-fluoropyridine (FPy) with high dipole preferentially adsorbs onto the Li metal surface. The adsorbed FPy molecule squeezes succinonitrile in the primary solvation sheath through steric hindrance, leading to the formation of an inorganic-rich interphase. Consequently, the introduction of FPy enhances the reversible capacity of the LiCoO₂||Li cell, which maintains a capacity of 143 mAh g⁻¹ after 500 cycles at a 1 C rate. Moreover, the cycle life of LiCoO₂ batteries with a limited supply of lithium extends from 120 cycles to over 200 cycles. These findings offer a strategy that can be applied broadly to design interfacial solvation structures for various metal-ion/metal-based batteries.