LiNO3 Nanoparticle Enabled Solvent Confinement and a Favorable Li+ Solvation Environment in Ester Electrolytes for Anode-Free Lithium Metal Batteries

Manipulating the solvation environment of lithium ions (Li+) in liquid electrolytes is crucial for achieving a stable solid electrolyte interphase (SEI) layer on lithium metal anodes. In this work, we report a method to regulate the Li+ solvation environment in ester-based electrolytes by incorporating lithium nitrate (LiNO3) nanoparticles as an additive. The dipole–dipole interactions at the LiNO3 particle/electrolyte interface result in ordered aggregation of solvent molecules on the surface of LiNO3 particles, forming a molecular confinement layer that drives the formation of a weak Li+ solvation environment. This enables Li+ to bind more readily with anions, facilitates rapid Li+ conduction, and promotes an inorganic-rich SEI. Electrochemical tests show that such changes induced by LiNO3 nanoparticles significantly enhance the Coulombic efficiency, reduce lithium nucleation overpotential, suppress lithium dendrite growth, and extend the cycle life of anode-free cells. Besides, with 6000 ppm of H2O in the electrolyte, cells achieve stable cycling for over 200 cycles with a capacity retention of 71.21%. These findings provide insights into solvent/ion regulation at solid/liquid interfaces in advanced electrolytes.