Constructing heterointerface of Bi/Bi2S3 with built-in electric field realizes superior sodium-ion storage capability

Bismuth sulfide (Bi₂S₃) is a dominant anode material for sodium-ion batteries due to its high theoretical capacity. However, extreme volume fluctuations as well as low electrical conductivity and reaction kinetics still limit its practical applications. Herein, we construct an abundant heterointerface of Bi/Bi₂S₃ by engineering the structure of Bi nanoparticles embedded on Bi₂S₃ nanorods (denoted as Bi–Bi₂S₃ NRs) to effectively solve the abovementioned obstacles. Theoretical and systematic characterization results reveal that the constructed heterointerface of Bi/Bi₂S₃ has a built-in electric field, significantly boosts the electrical conductivity, enhances the Na⁺ diffusion kinetics, and buffers the volume variation. With this modification, it can deliver long cycling life, with an ultra-high capacity of 500 mAh g⁻¹ over 500 cycles at 1 ​A ​g⁻¹, and outstanding rate capability, with a capacity of 456 mAh g⁻¹ even at 15 ​A ​g⁻¹. Moreover, a full cell can achieve a high energy density of 180 ​Wh kg⁻¹ at a power density of 40 ​W ​kg⁻¹. Our research opens up a fresh path for improving the dynamics and structural stability of metal sulfide-based electrode materials for SIBs.