Exploring sodium storage mechanism of topological insulator Bi2Te3 nanosheets encapsulated in conductive polymer

Topological insulator has attracted worldwide attention due to its promising application prospects in magnetoresistive devices, optoelectronic devices, spintronic and quantum computing. Nevertheless, its potential in electrochemical energy storage have not been fully explored and utilized. In this paper, a composite of high conductive polypyrrole encapsulated Bi2Te3, a hexagonal phase topological insulator, was synthesized by one-step solvothermal method, and its electrochemical properties were extensively studied. Benefiting from the inherent characteristics of topological insulator, the effective polypyrrole coating, and the intrinsic large interplanar spacing within Bi2Te3, the obtained Bi2Te3@PPy composite exhibited high specific capacity, high-rate capability, and long-term cyclic stability compared with other Bi-based materials in sodium ion batteries system. Furthermore, the reaction mechanism of conversion combined with alloying for Bi2Te3@PPy was revealed by in-situ XRD and ex-situ TEM techniques. The DFT calculations shown that the sandwiching interlayer between Bi2Te3 and PPy would familiar to the Na+ transfer, and the narrowing band gap would enhance the conductivity of the system, which will not only help us to better understand the sodium storage mechanism and reaction kinetics of Bi2Te3, but also provides a reliable strategy for the development of topological insulator as sodium-ion batteries anode materials.