Flexible Ti₃ C₂ T_x MXene Bonded Bio-Derived Carbon Fibers Support Tin Disulfide for Fast and Stable Sodium Storage

High energy density and flexible electrodes, which have high mechanical properties and electrochemical stability, are critical to the development of wearable electronics. In this work, a free-standing MXene bonded SnS₂ composited nitrogen-doped carbon fibers (MXene/SnS₂ @NCFs) film is reported as a flexible anode for sodium-ion batteries. SnS₂ nanoparticles with high-capacity properties are covalently decorated in bio-derived nitrogen-doped 1D carbon fibers (SnS₂ @NCFs) and further assembled with highly conductive MXene sheets. The addition of bacterial cellulose (BC) can further improve the flexibility of the film. The unique 3D structure of points, lines, and planes can not only offset the disadvantage of low conductivity of SnS₂ nanoparticles but also expand the distance between MXene sheets, which is conducive to the penetration of electrolytes. More importantly, the MXene sheets and N-doped 1D carbon fibers (NCFs) can accommodate the large volume expansion of SnS₂ nanoparticles and trap polysulfide during the cycle. The MXene/SnS₂ @NCFs film exhibits better sodium storage and excellent rate performance compared to the SnS₂ @NCFs. The in situ XRD and ex situ (XRD, XPS, and HRTEM) techniques are used to analyze the sodiation process and to deeply study the reaction mechanism of the films. Finally, the quasi-solid-state full cells with MXene/SnS₂ @NCFs and Na₃ V₂ (PO₄ )₃ @carbon cloth (NVP@CC) fully demonstrate the application potential of the flexible electrodes.