Effects of Ga–Ba Co-doping on the morphology and conductivity of Li₇La₃Zr₂O₁₂ electrolyte synthesized by sol-gel method

The garnet electrolyte Li₇La₃Zr₂O₁₂ with excellent electrochemical properties is one of the crucial materials in all-solid-state batteries. However, the abnormal grain growth (AGG) phenomena easily occurring during sintering process could damage the mechanical strength of the electrolyte. In this paper, a series of Ga–Ba co-doping LLZO samples, Li_{7-3x + y}Ga_xLa_3-yBa_yZr₂O₁₂ (x = 0.25 and y = 0.01, 0.03, 0.05, 0.15, 0.25, 0.35, 0.45, LGBLZO), were synthesized through sol-gel method to investigate the effects of Ba content on phase, morphology and ionic conduction in ceramics. The results demonstrated the influence mechanism of Ba ions in LGBLZO ceramics as follows. Firstly, the Ba ions as substitution of La sites could regulate the concentration of Li ions in lattice, reducing the bulk resistance. Secondly, the BaZrO₃ embedded between grains could prevent abnormal growth of grains effectively. These ceramics acquired optimal relative density after sintering at 1160 °C for 15 h. When the Ba ions feed ratio reaches 0.25 pfu, the LGBLZO (y = 0.25) exhibits excellent performance with a relative density of 94.8%, an ionic conductivity of 8.30 × 10⁻⁴S/cm and an activation energy of 0.228eV. Above researches provide ideas for the preparation of compact LLZO ceramics with uniform grain size and outstanding properties.