High Ionic Conductivity in Li2ZrCl6 via La3+ Doping for All-Solid-State Lithium Metal Batteries

Halides not only possess high ionic conductivity but also exhibit excellent electrochemical stability against high-voltage cathodes, making them promising candidates for solid-state electrolytes in all-solid-state lithium metal batteries (ASSLMBs). Compared with rare-earth halide electrolytes, Li 2 ZrCl 6 electrolytes are less costly. However, they face challenges relating to relatively lower ionic conductivity. Herein, Li 2+ x Zr 1− x La x Cl 6 is synthesized through La 3+ doping in Li 2 ZrCl 6 . The introduction of La 3+ increases the concentration of lithium ions in the crystal and expands the lattice volume, leading to ionic conductivity as high as 8.22 × 10 −4  S cm −1 . When Li 2.1 Zr 0.9 La 0.1 Cl 6 is applied in ASSLMBs (with a LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode and a Li-In anode), it exhibits superior electrochemical performance, with high initial capacity of 132.5 mA h g −1 , and after 100 cycles at 0.5 C, the battery still maintains a capacity of 72.4 mA h g −1 and high coulombic efficiency of 99.7%. Graphical