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.