Metal-phosphide-doped Li₇P₃S₁₁ glass-ceramic electrolyte with high ionic conductivity for all-solid-state lithium-sulfur batteries

Novel glass-ceramic electrolytes of (100-x) (70Li₂S-30P₂S₅)-xNi₂P (x = 0, 1, 2, 3, 4) with high ionic conductivity were proposed with the addition of Ni₂P. The 2 mol% Ni₂P containing electrolyte (Li₇Ni_0.2P_3.1S₁₁) displays the highest lithium-ion conductivity of 2.22 mS cm⁻¹ at room temperature, which is 1.6 times higher than pristine Li₇P₃S₁₁. By direct combination with Li₂S, the fabricated Li₇Ni_0.2P_3.1S₁₁-Li₂S all-solid-state battery exhibits an initial discharge capacity of 429 mAh g⁻¹ at 0.064 mA cm⁻² and 454 mAh g⁻¹ at 20th charging/discharging cycle with a high Coulombic efficiency of 99.7%.