Dynamic Gradient Oxygen Layer Enables Stable Sn Anode for Lithium Storage

Abstract Sn‐based anodes are of significant interest due to their high capacity and resource abundance for lithium‐ion batteries. However, incomplete lithiation and severe volume expansion result in their low capacity and electrode pulverization. Here, a rationally designed coating layer, composed of disordered SnO x (x = 1, 2) lamellar structures, on the Sn particles surface (Sn@SnO x ) is proposed. This coating effectively mitigates volume expansion and minimizes lithium consumption owing to the intercalation behaviors of SnO x . During lithiation and delithiation, a dense, amorphous, mechanical coating with a dynamic gradient of oxygen forms in situ, providing excellent protection against continuous pulverization of the Sn particles. The intercalation‐type dynamic gradient oxygen with high ionic conductivity enables rapid exchange of lithium ions, thus promoting the deep lithiation of Sn to form Li 4.4 Sn. Such gradient oxygen protection mechanism of the oxide layer in Sn@SnO x brings a high reversible capacity after 900 cycles with a capacity retention of 84%. This work offers a new strategy to design a protective coating layer on alloy‐based anodes for high‐performance lithium storage.