Oxygen‐Driven Structural Reorganization by Trace Water Enabling Fast Li‐Ion Transport in a Pliable Solid Electrolyte

ABSTRACT The hygroscopic property of solid electrolytes has long been regarded as a critical weakness, as exposure to ambient humidity typically induces decomposition and a loss of ionic conductivity. In this study, we reveal a counterintuitive yet constructive role of trace water in enhancing ion transport in a gallium‐based pliable halide solid electrolyte. Controlled exposure of 2LiCl–GaF 3 to trace amounts of water introduces oxygen into the structure and reorganizes the local environments around gallium and lithium. This oxygen‐driven structural reconfiguration forms Ga–O and Li–O linkages and diversifies the local environment of gallium by converting its coordination from sixfold to fourfold. It reduces the average Li–anion binding strength and flattens the Li‐ion migration energy landscape, resulting in enhanced Li‐ion transport. These changes collectively increase the ionic conductivity by more than two orders of magnitude, from 10 −2 mS cm −1 to over 3 mS cm −1 , while imparting amorphous and deformable characteristics to the 2LiCl‐GaF 3 electrolyte. This study demonstrates that the interaction between trace water and complex anion frameworks can be harnessed to simultaneously tailor structural and transport properties, offering a new design strategy for high‐performance oxyhalide solid electrolytes.