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

Abstract

Solid‐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.

Advancements in cathode materials for potassium-ion batteries: current landscape, obstacles, and prospects

“…439 Despite the existence of polymer electrolytes exhibiting high K + conductivity, the literature on solid-state potassium-ion conductors remains relatively scarce. 443–476 As a result, the current focus of research revolves around enhancing the ionic conductivity of solid-state potassium-ion conductors. However, it is essential to note that other pivotal electrochemical properties often remain insufficiently characterised, including electrochemical stability, ion selectivity, mechanical properties, and assembly techniques.…”