Se doping and spatial confinement promote solid-solid conversion kinetics of BiSSe-SSePAN for efficient...

Bismuth sulfide (Bi₂S₃), known for its high capacity, has been considered a promising anode material for high-performance sodium/potassium-ion batteries (SIBs/PIBs). However, the practical application of Bi₂S₃ is limited by its poor intrinsic electrical conductivity, significant volume fluctuations and sluggish reaction kinetics. The synergistic strategy of confinement engineering and heteroatom doping can effectively address these issues. Herein, a composite material of selenium-substituted Bi₂S₃ (BiSSe) embedded in selenium-substituted sulfurized polyacrylonitrile (SSePAN) is successfully synthesized (denoted as BiSSe-SSePAN). The incorporation of selenium significantly enhances the electrical conductivity of the material and accelerates the redox conversion of sulfur. Moreover, the confinement effect of the SSePAN matrix effectively prevents the agglomeration of BiSSe nanoparticles and mitigates volume variations. The BiSSe-SSePAN anode demonstrates outstanding sodium/potassium storage performance, achieving a high reversible capacity, superior rate capability, and prolonged cycle lifespan (e.g. 275 mAh g^-1/38000 cycles/15 A g^-1 in SIBs). Notably, BiSSe-SSePAN can operate stably over a wide temperature range (-15 °C to 50 °C). The assembled BiSSe-SSePAN//Na₃V₂(PO₄)₃ (NVP) full cell delivers a stable capacity of 375 mAh g^-1 over 500 cycles at 2 A g^-1. It is worth noting that the BiSSe-SSePAN//NVP pouch cell exhibits a high capacity of 146 mAh after 400 cycles at 0.1 A g^-1, confirming its potential for practical applications. This work provides an innovative insight into advancing the performance of metal sulfides in pouch cells and wide temperature workability.