Enhancing Ionic Conductivityin Li₃NbO₄ through Cl^– IonDoping: Reduced DiffusionBarriers

Li₃NbO₄ exhibits a high theoretical lithium-ion conductivity and a wide electrochemical window, positioning it as a promising solid electrolyte material with significant potential applications. Nevertheless, its actual conductivity lags behind theoretical expectations. Doping Li₃NbO₄ with large-radius Cl^– ions is anticipated to widen the ionic diffusion pathways by substituting O^2– ions and decrease the binding energy of lithium ions within the coordination polyhedra, thereby boosting its ionic conductivity. In this investigation, various Cl^– doped electrolytes of Li_{3–3<i>x</i>}NbO_{4–3<i>x</i>}Cl_3<i>x</i> (<i>x</i> = 0, 0.04, 0.08, 0.12) were synthesized using conventional techniques. The findings reveal that the ionic conductivity of Li_2.76NbO_3.76Cl_0.24, produced by incorporating 8 mol % Cl^– into the Li₃NbO₄ framework, achieves 3.95 × 10^–4 S cm^–1 at room temperature, marking a two-order-of-magnitude enhancement over the original Li₃NbO₄ sample (8.35 × 10^–6 S cm^–1). When this electrolyte powder is integrated into a LiNi_0.5Co_0.2Mn_0.3O₂ cathode material to create a coin cell, the addition of 3 wt % Li_2.76NbO_3.76Cl_0.24 significantly enhances the lithium-ion diffusion coefficient on the positive side of the battery, curtails irreversible lithium-ion loss during battery cycling, and showcases exceptional cyclic stability.