Solid-state ion doping and crystal structure engineering for enhanced ionic conductivity in LiTi 2 (PO 4 ) 3 electrolytes

NASICON-type LiTi 2 (PO 4 ) 3 (LTP) are gaining enormous attention for applications in solid-state lithium-ion batteries due to its comparatively high conductivities and three-dimensional open-framework. The selective substitution strategies at cationic sites are regarded as an important approach to enhance the ionic conductivity of LTP electrolytes. Present work reports the influence of Ga 3+ ions doping on the crystal structure, density, activation energy, and ionic conductivity of Li 1+ x Ga x Ti 2– x (PO 4 ) 3 ( x = 0, x = 0.25, x = 0.5, x = 0.75 and x = 1, labeled as LGTP) electrolytes. Herein, we found that the relative density, activation energy, and conductivity of LGTP electrolytes show a tendency to increase first and then decrease as Ga 3+ doping increases. The sample with x = 0.5 exhibits the highest ionic conductivity (4.64 × 10 –4 S cm −1 ), the highest relative density (96.21%), and the lowest activation energy (0.17 eV). The conductivity of Li 1.5 Ga 0.5 Ti 1.5 (PO 4 ) 3 (LGTP050) increases by three orders of magnitude when compared to LTP without Ga 3+ doping, possibly due to its high relative density, low activation energy, and high lithium-ion concentration. These findings suggest that doping LTP ceramic electrolytes with Ga 3+ can significantly improve conductivity.