High ionic conductivity of Li3-2xMxPS4 (M = Ca or Mg) at high temperature

Li3-2xMxPS4 (M = Ca or Mg) solid electrolytes were prepared by planetary ball-milling. Solid electrolytes that were amorphous in XRD were obtained with 0 <= x <= 0.115. A new crystalline phase was detected in samples with x >= 0.391. The addition of Ca2+ to the Li3PS4 matrix (x <= 0.115) resulted in reduction of the total conductivity at room temperature but conductivity enhancement was obtained at temperatures of 50 degrees C or higher. The sample Li2.88Ca0.06PS4 exhibited conductivity of about 9 mS cm(-1) at 90 degrees C, which was much improved compared with the conductivity of intrinsic Li3PS4 (2 mS cm(-1)).