Realizing Ultrahigh Cycle Life Anode for Sodium-Ion Batteries through Heterostructure Design and Introducing Electro Active Polymer Coating

Bi₂S₃ has attracted increasing attention in sodium-ion batteries (SIBs) for its high theoretical capacity and low discharge platform. However, the sodium storage performance of Bi₂S₃ is limited by poor electrical conductivity and volume expansion during cycling. Herein, we report a special polypyrrole (PPy)-coated MoS₂/Bi₂S₃ (MBS@PPy) heterostructure composite obtained by hydrothermal reaction as an anode material for SIB. As a result, the MBS@PPy composites demonstrate exceptional electrochemical performance in SIB, exhibiting a high capacity of 361.1 mA h g^–1 at 10 A g^–1 and showcasing remarkable rate performance. Even under a high current density of 35 A g^–1, the specific capacity remains stable at 280 mA h g^–1 after 2,000 cycles. Furthermore, a successfully assembled Na₃V₂(PO₄)₃//MBS@PPy sodium-ion full cell can achieve an impressive specific capacity of approximately 400 mA h g^–1 after 300 cycles at 0.5 A g^–1. In MBS@PPy composites, the polypyridine coating not only improves the interfacial conductivity of nanorods but also effectively inhibits the agglomeration between nanorods due to large volume changes. The MoS₂ heterostructure further inhibits the coarsening of the internal structure, improves electron transport and reaction kinetics, and increases the rate capability of the material. This work provides an effective strategy to develop energy storage materials with superior electrochemical properties.