Magnesium-lithium hybrid batteries (MLHBs) have gained increasing attention due to their combined advantages of rapid ion insertion/extraction cathode and magnesium metal anode. Herein, SnS₂-SPAN hybrid cathode with strong C-Sn bond and rich defects is ingeniously constructed to realize Mg²⁺/Li⁺ co-intercalation. The physical and chemical double-confinement synergistic engineering of sulfurized polyacrylonitrile can suppress the agglomeration of SnS₂ nanoparticles and the volume expansion, simultaneously promote charge transfer and enhance structural stability. The introduced abundant sulfur vacancies provide more active sites for Mg²⁺/Li⁺ co-intercalation. Meanwhile, the beneficial effects of rich sulfur defects and C-Sn bond on enhanced electrochemical properties are further evidenced by density-functional theory (DFT) calculations. Therefore, compared with pristine SnS₂, SnS₂-SPAN cathode displays high specific capacity (218 mAh g⁻¹ at 0.5 A g⁻¹ over 700 cycles) and ultra-long cycling life (101 mAh g⁻¹ at 5 A g⁻¹ up to 28,000 cycles). And a high energy density of 307 Wh kg⁻¹ can be realized by the SnS₂-SPAN//Mg pouch cell. Such elaborate and simple design supplies a reference for the exploitation of advanced cathode materials with excellent electrochemical properties for MLHBs.