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 Li7-x+yLa3Zr2-x-yNbxGdyO12 (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, Li6.5La3Zr1.3Nb0.6Gd0.1O12 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 Li6.5La3Zr1.3Nb0.6Gd0.1O12. 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/Li6.5La3Zr1.3Nb0.6Gd0.1O12, 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.