LaCl-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-based Na superionic conductor (NaZrLaCl) with high ionic conductivity of 2.9 × 10S cm (30 °C), good compressibility and high oxidative potential (3.80 V vs. NaSn) is prepared via solid state reaction combining mechanochemical method. X-ray diffraction reveals a hexagonal structure (P6/m) of NaZrLaCl, 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 NaZrLaCl is mainly determined by the size of Na-channels and the Na/La mixing in the one-dimensional diffusion channels. When applied as a catholyte, the NaCrO||NaZrLaCl||NaPS||NaSn all-solid-state batteries demonstrate an initial capacity of 114 mA h g and 88% retention after 70 cycles at 0.3 C. In addition, a high capacity of 94 mA h g can be maintained at 1 C current density.