In Situ Atomic-Scale Observation of Reversible Potassium Storage in Sb2S3@Carbon Nanowire Anodes

Antimony trisulfide-based materials have drawn growing attention as promising anode candidates for potassium-ion batteries (PIBs) because of their high capacity and good working potential. Despite the extensive investigations on their electrochemical properties, the fundamental reaction mechanisms of Sb(2)S(3)anodes, especially the reaction kinetics, structural changes, and phase evolutions, remain controversial or even largely unknown. Here, using in situ transmission electron microscopy, the entire potassiation-depotassiation cycles of carbon-coated Sb(2)S(3)single-crystal nanowires are tracked in real time at the atomic scale. The potassiation of Sb(2)S(3)involves multistep reactions including intercalation, conversion, and two-step alloying, and the final products are identified as cubic K2S and hexagonal K3Sb. These findings are confirmed by density functional theory calculations. Interestingly, a rocket-launching-like nanoparticle growth behavior is observed during alloying reactions, which is driven by the K(+)concentration gradient and release of stress. More impressively, the potassiated products (i.e., K3Sb and K2S) can transform into the original Sb(2)S(3)phase during depotassiation, indicating a reversible phase transformation process, as distinct from other metal chalcogenide based electrodes. This work reveals the detailed potassiation/depotassiation mechanisms of Sb2S3-based anodes and can facilitate the analysis of the mechanisms of other metal chalcogenide anodes in PIBs.