LaCl 3 -based sodium halide solid electrolytes with high ionic conductivity for all-solid-state batteries.

To enable high performance of all solid-state batteries, a catholyte should demonstrate high ionic conductivity, good compressibility and oxidative stability. Here, a LaCl ₃ -based Na ⁺ superionic conductor (Na _{1 - x} Zr _x La _{1 - x} Cl ₄ ) with high ionic conductivity of 2.9 × 10 ^-4 S cm ^-1 (30 °C), good compressibility and high oxidative potential (3.80 V vs. Na ₂ Sn) is prepared via solid state reaction combining mechanochemical method. X-ray diffraction reveals a hexagonal structure (P6 ₃ /m) of Na _{1 - x} Zr _x La _{1 - x} Cl ₄ , with Na ⁺ ions forming a one-dimensional diffusion channel along the c-axis. First-principle calculations combining with X-ray absorption fine structure characterization etc. reveal that the ionic conductivity of Na _{1 - x} Zr _x La _{1 - x} Cl ₄ is mainly determined by the size of Na ⁺ -channels and the Na ⁺ /La ³⁺ mixing in the one-dimensional diffusion channels. When applied as a catholyte, the NaCrO ₂ ||Na _0.7 Zr _0.3 La _0.7 Cl ₄ ||Na ₃ PS ₄ ||Na ₂ Sn all-solid-state batteries demonstrate an initial capacity of 114 mA h g ^-1 and 88% retention after 70 cycles at 0.3 C. In addition, a high capacity of 94 mA h g ^-1 can be maintained at 1 C current density.
(© 2024. The Author(s).)