Isomorphism of LiV₃O₈/NaV₃O₈ and Its Li⁺ Transport Behavior

Distinct physical and chemical properties are shown for the bulk and surface of the electrodes, resulting in different ion diffusion behaviors. The knock-off mechanism for multi-ion cooperative transport of LiV₃O₈ exhibits excellent solid diffusion kinetics, but the slow Li⁺ insertion at the electrode/solution interface becomes the rate-controlling step of the reaction. The direct-hopping mechanism is more favorable for Li⁺ insertion reactions at the electrode/solution interface. The isomorphic LiV₃O₈/NaV₃O₈ with a core-shell structure synthesized by the ion exchange method combines the advantages of the knock-off and direct-hopping diffusion mechanisms. For Li⁺ transport at the surface phase (NaV₃O₈), the direct-hopping mechanism is adopted for the lower energy barriers, and for Li⁺ transport in the bulk phase (LiV₃O₈), the knock-off mechanism is used to achieve high-rate solid diffusion. The activation energy of the interfacial reaction decreases from the original 35.47 kJ mol^-1 to 26.25 kJ mol^-1, and the Li⁺ intercalation energy barrier at the electrode/solution interface decreases from the original 0.61 to 0.40 eV. LiV₃O₈ and NaV₃O₈, belonging to the isomorphic group, have similar chemical compositions and lattice parameters, demonstrating high lattice matching and core-shell binding forces. The core-shell structure of LiV₃O₈/NaV₃O₈ with a fast ion transport rate exhibits excellent rate performance.