Ultrahigh‐Rate and Long‐Cycle Sodium‐Ion Batteries via Heterojunctions of Bimetallic/Monometallic Sulfides on N‐Doped Carbon Nanotubes

Abstract Sodium‐ion batteries (SIBs) hold great promise for large‐scale energy storage due to their low cost and safety, but their development is limited by the lack of high‐performance anode materials. To overcome this, a heterostructured CoNi₂S₄/NiS composite anchored on nitrogen‐doped carbon nanotubes (CoNi₂S₄/NiS@CNTs) is designed via an in‐situ growth, carbonization, and sulfurization strategy. This architecture ensures strong coupling between sulfides and a 3D conductive CNT network, enhancing Na⁺ storage kinetics and structural stability. CoNi₂S₄ facilitates continuous ion transport, while NiS increases the density of states near the Fermi level, boosting multi‐electron redox reactions. A built‐in electric field at the heterojunction interface, combined with the CNT network, reduces the Na⁺ diffusion barrier to 1.09 eV. The N‐doped CNTs mitigate surface degradation and suppress polysulfide shuttling through physical confinement, chemical adsorption, and mechanical reinforcement. As a result, the anode delivers an ultra‐stable reversible capacity of 285.6 mAh g⁻¹ after 45 000 cycles at 50 A g⁻¹ with nearly 100% retention. Even at −20 °C, it retains 655.93 mAh g⁻¹ after 80 cycles. This work establishes a new paradigm for designing high‐rate, long‐life SIBs anodes through multi‐scale structural engineering and conductive frameworks.