Helical carbon nanofibers anchored SnO2/SnSe2 heterojunction host synergistically enhances polysulfide adsorption and catalysis for high performance lithium‑sulfur batteries

Work-function differences between SnO 2 and SnSe 2 induces interfacial band bending and constructing a built-in electric field • The BIEF enriches electrons on Sn sites for strong adsorption, while populating Li- S antibonding orbitals to weaken the bonds • Complementary barriers of SnO 2 /SnSe 2 with HCNF anchoring/buffering enable Li-S battery high capacity and long cycling The shuttle effect and sluggish conversion kinetics of polysulfides severely hinder the practical application of lithium‑sulfur (Li S) batteries. In this work, a novel SnO 2 /SnSe 2 heterostructure anchored on helical carbon nanofibers (HCNFs) is designed and fabricated as a sulfur cathode host (SnO 2 /SnSe 2 @HCNFs//S). The differences in electronegativity and ionic radius between oxygen and selenium drive interfacial electron transfer and generate a built-in electric field (BIEF), endowing the heterojunction with an electronic configuration that combines strong overall adsorption and weak Li S bonds, thereby breaking the conventional balances between adsorption strength and catalytic activity. SnO 2 exhibits a lower energy barrier for the S 8 to Li 2 S n conversion, while SnSe 2 shows a lower barrier for the Li 2 S n to Li 2 S conversion, demonstrating complementary functions, and the BIEF further reduces the overall energy barrier of the multistep reduction to the lowest level. The defect sites of the helical carbon fibers ensure highly dispersed loading of the heterojunction, and the spring-like helical morphology buffers volume expansion and maintains long-term cycling stability. The SnO 2 /SnSe 2 @HCNFs//S cathode delivers an outstanding discharge specific capacity of 1008.2 mAh g −1 at 0.2C, retains over 99.7% of coulombic efficiency after 200 cycles at 0.2C, and a rate performance of 932.4 mAh g −1 even at 2.0C, with rate and cycling performance significantly superior to those of single-phase materials and control samples. This work provides an effective strategy for the rational design of high-performance sulfur hosts for Li S batteries. Helical carbon nanofibers (HCNFs) with abundant defect sites serve as a substrate for anchoring SnO 2 /SnSe 2 heterojunction nanoparticles, ensuring highly dispersed exposure. Work function mismatch drives electron transfer from SnSe 2 to SnO 2 , enhancing Sn S adsorption while injecting electrons into Li S antibonding orbitals to weaken bonds. SnO 2 lowers reaction barrier from S 8 to Li 2 S n , and SnSe 2 lowers barrier from Li 2 S n to Li 2 S, and the built-in electric field further reduces the multistep energy barrier of sulfur conversions, thereby achieving efficient polysulfide adsorption and catalytic conversion. Download: Download high-res image (295KB) Download: Download full-size image