Unlocking Ultralong Cycle Life and Temperature-Tolerable Secondary Batteries Using a Vacancy-Abundant Co ₉ S ₈ @ZnS/Carbon Anode

Sodium-ion batteries face some critical anode-level barriers: sluggish Na⁺ transport, conversion-induced instability, and poor temperature adaptability. Here, we develop a vacancy-based synergy in Co₉S₈@ZnS/C synthesized by metal-organic framework-templated sulfidation. The Co-Zn-S system provides sodiophilic vacancies that lower Na⁺ diffusion barriers and further strengthen the interfacial field. This self-reinforcing synergy is validated through in situ X-ray diffraction and in situ Raman spectroscopy, demonstrating reversible conversion/alloying and interfacial reconstruction. The Co₉S₈@ZnS/C anode delivers exceptional performance, including a high capacity of 458.7 mAh g⁻¹ after 400 cycles at 1.0 A g⁻¹ and a remarkable ultralong stability of 249.1 mAh g⁻¹ after 4000 cycles at 15.0 A g⁻¹, with robust operation from -10 to 50 °C. Full cells paired with Na₃V₂(PO₄)₃ demonstrate excellent stability, validating their practical viability. This work establishes a generalizable vacancy-abundant design principle that deterministically links defect thermodynamics and electrostatics to long-term Na storage across diverse operating conditions.