A Robust Metal‐Organic Framework Derived Bioinspired Metal‐Polyphenol Network Interface for Enhanced Sodium Storage

ABSTRACT The development of flexible anode materials for sodium‐ion batteries (SIBs) is crucial for next‐generation flexible and wearable electronics. However, conventional flexible current collectors such as carbon cloth and aerogels still suffer from poor interfacial stability and limited mechanical properties. Inspired by biomineralization principles, a bionic metal‐phenolic network (MPN) interfacial engineering is introduced to achieve controllable integration of metal‐organic framework (MOF) coatings on flexible substrates. A one‐step calcination‐sulfidation treatment transforms the MOF precusor into uniformly dispersed high‐capacity Fe ₇ S ₈ nanoparticles anchored on carbonized silk fabric. The MPN self‐assembled through coordination between tannic acid and Fe ³⁺ , directs uniform growth of MIL‐88A, and subsequently converts into an amorphous carbon shell. This carbon interlayer provides strong anchoring of active materials, forms continuous electron‐transport pathways, and enhances interfacial stability. The optimized MSMF‐2 composite maintains structural integrity after 2000 bending cycles and retains a specific areal capacity of 1.40 mAh cm ⁻² after 200 cycles at 0.3 mA cm ⁻² , while demonstrating 97.3% capacity retention after 1000 cycles at 5 mA cm ⁻² . Furthermore, solid electrolyte interphase composition and phase‐transition mechanisms are systematically investigated, revealing stable interfacial passivation and dual intercalation–conversion storage behavior. This work demonstrates an effective strategy that integrates biomimetic interfacial regulation with MOF‐derived active materials.