In Situ-Derived Bi4Ti3O12-Bi2S3 Ferroelectric-Semiconductor Heterojunction as a Multifunctional Separator Coating for Lithium-Sulfur Batteries.

The practical viability of lithium-sulfur batteries (LSBs) is severely hindered by sluggish liquid-solid conversion kinetics and the polysulfide shuttle effect. Herein, we report an in situ-derived ferroelectric-semiconductor Bi4Ti3O12-Bi2S3 heterojunction as a multifunctional separator coating. The intimate atomic-level coupling at the heterointerface generates a built-in electric field that, synergizing with the spontaneous ferroelectric polarization of Bi4Ti3O12, structurally intensifies polysulfide chemisorption and lowers the activation energy for bi-directional Li2S precipitation/dissociation. Furthermore, the localized polar field appears to homogenize lithium-ion flux, which may contribute to improved lithium anode stability. Consequently, cells featuring the modified separator deliver a high initial capacity of 1172 mAh g-1 at 0.5 C and demonstrate good cycling stability over 500 cycles with a low capacity decay rate of 0.096% per cycle. This in situ interfacial engineering offers a promising kinetic regulatory strategy for improving the performance of LSBs.