Ultrafast charge transfer at the electrode−electrolyte interface via an artificial dielectric layer

We report ultrafast charge transfer along the Li-ion pathway via a dielectric layer at the electrolyte−electrode interface. The rate capabilities of dielectric-modified cathodes were evaluated as a function of the combination of electrolyte solvents and dielectric layers having various dielectric constants, ε_r. The high-rate capability was enhanced when the loaded dielectric layer's ε_r was close to that of the electrolyte solvent. Density functional theory molecular dynamics calculations and atomic force microscope force measurements confirmed that the activation energies related to Li⁺ adsorption and desolvation were notably reduced when the loaded dielectric layer's ε_r approached that of the solvent. In this case, the solvated Li⁺ ion preferentially underwent desolvation on the solid surface. The discharge capacity at the ultrahigh rate of 50 C (1 C = 160 mA g⁻¹) of the dielectric-modified thin films steadily increased with increasing length of the dielectrics−electrode−electrolyte triple-phase interface (TPI). Experimental and computational results reveal that, when the permittivity of the dielectrics and solvent are similar, solvated Li⁺ ions are preferentially involved in the physical adsorption and desolvation on the dielectric surface, followed by Li⁺ intercalation near the TPI.