Nonmonotonic Screening and Solvation Dynamics of the Electrical Double Layer in Concentrated Lithium Salt Electrolytes

Abstract Understanding the electrical double layer in lithium-ion battery electrolytes is fundamental to improving interfacial processes that govern battery performance and lifetime. However, the microstructure and dynamics of the electrical double layer in highly concentrated lithium salt solutions remain elusive. Herein, combining electrochemical analyses, in situ gap-enhanced Raman spectroscopy and molecular dynamics simulations, we reveal nonmonotonic variation of electrostatic screening with concentration and different exchange kinetics of anions and solvent molecules in the solvation sheath of lithium ions. We find that increasing solvation entropy favors the formation of an anion-rich solvation environment in highly concentrated electrolytes, accelerating Li + –anion exchange relative to Li + –solvent exchange. This dynamic coordination behavior enables Li + to reorganize its solvation structure more readily during intercalation and deintercalation, thereby improving the kinetics and reversibility of these processes. Overall, this work provides thermodynamic and kinetic insights for the electrolyte design of advanced lithium-ion battery systems.