Synergistic effect of Ga and Yb co-doping on the structure and ionic conductivity of Li7La3Zr2O12 ceramics

Li 7 La 3 Zr 2 O 12 (LLZO) has shown excellent electrochemical performance and chemical stability. In this work, Li 6.4 Ga 0.2 La 3-x Yb x Zr 2 O 12 (0 ≤ x ≤ 0.1) has been synthesized by solid-state reaction method. The effect of Ga and Yb co-doping on the crystal structure, morphology, densification, and electrical performance was investigated. The doping with Ga 3+ stabilized the cubic phase while the doping with Yb 3+ optimized Li + transport channel size and accelerated the densification of the ceramics. Li 6.4 Ga 0.2 La 2.95 Yb 0.05 Zr 2 O 12 (relative density 94.8%) exhibited the highest total conductivity (8.96 × 10 −4 S·cm −1 at 30 °C) and the lowest activation energy of 0.28 eV. Meanwhile, Li 6.4 Ga 0.2 La 2.95 Yb 0.05 Zr 2 O 12 showed high mobility (1.36 × 10 −6 cm 2 V −1 s −1 ), diffusion coefficient (3.18 × 10 −8 cm 2 s −1 ) and high hopping rate of lithium ions (5.0 × 10 6 rad s −1 ) at 0 °C. The high discharge capacity and capacity retention of LiFePO 4 /Li 6.4 Ga 0.2 La 2.95 Yb 0.05 Zr 2 O 12 /Li solid-state batteries indicate that Ga and Yb co-doped Li 7 La 3 Zr 2 O 12 ceramic should be a promising electrolyte.