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.