K3SbS4 as a Potassium Superionic Conductor with Low Activation Energy for K–S Batteries

Abstract

AbstractSolid‐state K‐ion conducting electrolytes are key elements to address the current problems in K secondary batteries. Here, we report a sulfide‐based K‐ion conductor K3SbS4 with a low‐activation energy of 0.27 eV. W‐doped K3−xSb1−xWxS4 (x=0.04, 0.06, 0.08, 0.10 and 0.12) compounds were also explored for increasing vacancy concentrations and improving ionic conductivity. Among them, K2.92Sb0.92W0.08S4 exhibits the highest conductivity of 1.4×10−4 S cm−1 at 40 °C, which is among the best reported potassium‐ion conductors at ambient temperature. In addition, K2.92Sb0.92W0.08S4 is electrochemically stable with long‐chained potassium polysulfide of K2Sx. A room‐temperature solid potassium–sulfur (K−S) battery system has therefore been successfully demonstrated, which is the first K−S battery prototype using non‐commercial inorganic‐based electrolyte to block the polysulfide shuttle.