Abstract: The lithium content of Li₃NbO₄ is richer than that of ternary cathode materials. Adding Li₃NbO₄ to the ternary cathode materials can play a certain role in lithium supplementation, reduce the irreversible capacity of the battery and improve its cycle performance. However, the low room temperature ionic conductivity of Li₃NbO₄ limits its application. It is found that in the process of synthesizing Li₃NbO₄, the proportion of the face-centered cubic phase (Fm-3m) and body-centered cubic phase (I-43m) in the structure of the synthesized Li₃NbO₄ material can be adjusted by controlling the ratio of Li/Nb. The coexistence interface of the two phases can reduce the lithium-ion diffusion energy barrier and enhance the migration ability of lithium ions. The results show that when Li∶ Nb molar ratio is 3.6:1 in the composition, the I-43m phase accounts for the highest proportion of the obtained Li₃NbO₄ material, and the lithium-ion conductivity of the prepared sample is 35 times higher than that of the Fm-3m phase, reaching 8.35×10^-6 S/cm. The obtained high ionic conductivity Li₃NbO₄ powder is added to the ternary anode material to make LiNi_0.5Co_0.2Mn_0.3O₂/LiPF₆/Li coin cell. The resulting battery exhibits a 15% increase in specific capacity and demonstrates excellent long-cycling performance and high-rate capability.