Reducing the passivation layer of stable cubic phase Li7La3Zr1.6Hf0.4O12 electrolyte for high ionic conductivity

The development of Li 7 La 3 Zr 2 O 12 solid state electrolyte is retarded by its low ionic conductivity and surface passivation. A few studies suggest those two hurdles can be solved together. Capitalizing on similar physical and chemical properties of Hf 4+ and Zr 4+ , Hf 4+ doped Li 7 La 3 Zr 2- x Hf x O 12 ( x  = 0.3, 0.4, 0.5, and 0.6) is prepared and the influence of Hf 4+ on the structure and electrochemical performance of LLZO is investigated systematically. LLZO with Hf 4+ doping is transformed into cubic phase, and also reduces the secondary reaction between H 2 O, CO 2 and LLZO, while increasing the ionic conductivity of the electrolyte to 2.01 × 10 −4  S cm −1 . The electrochemical window between the LLZHO and lithium metal reaches 4.7 V, which is 0.8 V higher than that of LLZO. The specific capacity of the 1st discharge of the all-solid-state batteries assembled with the LiFePO 4 cathode at 0.1C reaches 110.00 mAh·g −1 . The coulombic efficiency reaches 99.18 % after 100 cycles, and the cycle retention rate is 65.82 %.