Lithium Superionic Conducting Oxysulfide Solid Electrolyte with Excellent Stability against Lithium Metal for All-Solid-State Cells

For the high-energy battery using Li metal as a negative electrode, the electrolyte is one of the most critical factors that significantly affects the cell performance. Herein, new 75Li(2)S center dot (25-x) P2S5 center dot xP(2)O(5) (mol%) solid state electrolytes are prepared by optimized mechanical milling technique and subsequent heat-treatment process. The electrolyte substituted with 1 mol% P2O5 presents the highest conductivity of 8 x 10(-4) S cm(-1) at room temperature, which increases up to 56% compared to that of the pristine sample. The enhanced conductivity could be attributed to the decrease of the activation energy for Li+-ion diffusion. The as-prepared 75Li(2)S center dot 24P(2)S(5) center dot 1P(2)O(5) electrolyte exhibits good electrochemical stability and compatibility with the metallic lithium electrode. The all-solid-state cell with a structure of LiCoO2/75Li(2)S center dot 24P(2)S(5) center dot 1P(2)O(5)/Li shows a discharge capacity of 109 mAh g(-1) at 0.1 C and high capacity retention 85.2% after 30 cycles at 25 degrees C, which are better than these of the cell use the 75Li(2)S center dot 25P(2)S(5) as electrolyte. (C) 2015 The Electrochemical Society.