Strain Retarding in Multilayered Hierarchical Sn-Doped Sb Nanoarray for Durable Sodium Storage

Antimony (Sb) is a potential electrode material for sodium (Na) storage due to its high theoretical capacity of 660 mAh g(-1). Yet, the alloy/dealloy reaction between Na and Sb induces detrimental structural strain that inevitably leads to electrode failure, further resulting in deteriorated rate performance and cycle life. Herein, inspired by the multilayered structure of the pine trees, 3D hierarchical multilayered tin (Sn)-doped Sb nanoarray coated with a thin carbon (C) layer (Sb(Sn)@C) is developed. Density functional theory calculation results suggest that Sb(Sn)@C offers better kinetic properties for Na diffusion, and lower volume expansion upon sodium intercalation as compared to the counterparts without Sn dopant or carbon coating. Moreover, the simulation results based on finite element analysis suggest that the unique hierarchical multilayered construction not only provides highly efficient Na+ utilization, but also builds a uniform von Mises stress distribution that effectively confines structural strain induced during Na+ insertion. This is also verified by nanoindentation measurement that Sb(Sn)@C shows higher elastic modulus and hardness than Sb(Sn) and pure Sb, indicating best mechanical stability. As expected, Sb(Sn)@C achieves excellent electrochemical capability for sodium storage with high reversible capacity, enhanced cyclability, and remarkable rate performance.