Effect of dual doping on the structure and performance of garnet-type Li₇La₃Zr₂O₁₂ ceramic electrolytes for solid-state lithium-ion batteries

Nb–Gd co-doping Li₇La₃Zr₂O₁₂ electrolytes with compositions of Li_7-x+yLa₃Zr_2-x-yNb_xGd_yO₁₂ (x = 0.6; y = 0, 0.05, 0.10 and 0.20) were prepared via solid-state reaction. The X-ray diffraction (XRD) and Raman spectra demonstrated that all compositions exhibited a single cubic structure. Among these prepared samples, Li_6.5La₃Zr_1.3Nb_0.6Gd_0.1O₁₂ sample presented the lithium-ion conductivity of 9.86 × 10⁻⁴ S cm⁻¹ when sintered at 1150 °C for 12 h. Meanwhile, bending strength and compressive strength reached 131 and 280.8 MPa, respectively. Further investigations were performed on the chemical and electrochemical properties of Li_6.5La₃Zr_1.3Nb_0.6Gd_0.1O₁₂. The XRD and cyclic voltammetry (CV) results showed that the ceramic sheet had excellent stability against metallic lithium and liquid electrolyte. A decrease in the interfacial resistance of Li/Li_6.5La₃Zr_1.3Nb_0.6Gd_0.1O₁₂, from 940 Ω cm² to 178 Ω cm², was observed. The full cells exhibited an initial discharge capacity of 138.5mAh g⁻¹, and the capacity remained at 130.8mAh g⁻¹ after 100 cycles.