Enhancing Ionic Conductivity in Li₃NbO₄ through Cl^– Ion Doping: Reduced Diffusion Barriers

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 O2– 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 Li3–3xNbO4–3xCl3x (x = 0, 0.04, 0.08, 0.12) were synthesized using conventional techniques. The findings reveal that the ionic conductivity of Li2.76NbO3.76Cl0.24, 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 LiNi0.5Co0.2Mn0.3O2 cathode material to create a coin cell, the addition of 3 wt % Li2.76NbO3.76Cl0.24 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.