Realizing Ultrahigh\nCycle Life Anode for Sodium-Ion\nBatteries through Heterostructure Design and Introducing Electro Active\nPolymer Coating

Bi<sub>2</sub>S<sub>3</sub> has attracted increasing\nattention\nin sodium-ion batteries (SIBs) for its high theoretical capacity and\nlow discharge platform. However, the sodium storage performance of\nBi<sub>2</sub>S<sub>3</sub> is limited by poor electrical conductivity\nand volume expansion during cycling. Herein, we report a special polypyrrole\n(PPy)-coated MoS<sub>2</sub>/Bi<sub>2</sub>S<sub>3</sub> (MBS@PPy)\nheterostructure composite obtained by hydrothermal reaction as an\nanode material for SIB. As a result, the MBS@PPy composites demonstrate\nexceptional electrochemical performance in SIB, exhibiting a high\ncapacity of 361.1 mA h g<sup>–1</sup> at 10 A g<sup>–1</sup> and showcasing remarkable rate performance. Even under a high current\ndensity of 35 A g<sup>–1</sup>, the specific capacity remains\nstable at 280 mA h g<sup>–1</sup> after 2,000 cycles. Furthermore,\na successfully assembled Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>//MBS@PPy sodium-ion full cell can achieve an impressive\nspecific capacity of approximately 400 mA h g<sup>–1</sup> after\n300 cycles at 0.5 A g<sup>–1</sup>. In MBS@PPy composites,\nthe polypyridine coating not only improves the interfacial conductivity\nof nanorods but also effectively inhibits the agglomeration between\nnanorods due to large volume changes. The MoS<sub>2</sub> heterostructure\nfurther inhibits the coarsening of the internal structure, improves\nelectron transport and reaction kinetics, and increases the rate capability\nof the material. This work provides an effective strategy to develop\nenergy storage materials with superior electrochemical properties.