Unveiling the Structural and Dynamic Characteristics of Concentrated LiNO₃ Aqueous Solutions through Ultrafast...

Highly concentrated aqueous electrolytes have attracted a significant amount of attention for their potential applications in lithium-ion batteries. Nevertheless, a comprehensive understanding of the Li⁺ solvation structure and its migration within electrolyte solutions remains elusive. This study employs linear vibrational spectroscopy, ultrafast infrared spectroscopy, and molecular dynamics (MD) simulations to elucidate the structural dynamics in LiNO₃ solutions by using intrinsic and extrinsic vibrational probes. The N-O stretching vibrations of NO₃^- exhibit a distinct spectral splitting, attributed to its asymmetric interaction with the surrounding solvation structure. Analysis of the vibrational relaxation dynamics of intrinsic and extrinsic probes, in combination with MD simulations, reveals cage-like networks formed through electrostatic interactions between Li⁺ and NO₃^-. This microscopic heterogeneity is reflected in the intertwined arrangement of ions and water molecules. Furthermore, both vehicular transport and structural diffusion assisted by solvent rearrangement for Li⁺ were analyzed, which are closely linked with the bulk concentration.