Ti3C2Tx MXene Conductive Layers Supported Bio‐Derived Fex−1Sex/MXene/Carbonaceous Nanoribbons for High‐Performance Half/Full Sodium‐Ion and Potassium‐Ion Batteries

Abstract Owing to their cost‐effectiveness and high energy density, sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs) are becoming the leading candidates for the next‐generation energy‐storage devices replacing lithium‐ion batteries. In this work, a novel Fe x −1 Se x heterostructure is prepared on fungus‐derived carbon matrix encapsulated by 2D Ti 3 C 2 T x MXene highly conductive layers, which exhibits high specific sodium ion (Na + ) and potassium ion (K + ) storage capacities of 610.9 and 449.3 mAh g −1 at a current density of 0.1 A g −1 , respectively, and excellent capacity retention at high charge–discharge rates. MXene acts as conductive layers to prevent the restacking and aggregation of Fe x −1 Se x sheets on fungus‐derived carbonaceous nanoribbons, while the natural fungus functions as natural nitrogen/carbon source to provide bionic nanofiber network structural skeleton, providing additional accessible pathways for the high‐rate ion transport and satisfying surface‐driven contribution ratios at high sweep rates for both Na/K ions storages. In addition, in situ synchrotron diffraction and ex situ X‐ray photoelectron spectroscopy measurements are performed to reveal the mechanisms of storage and de‐/alloying conversion process of Na + in the Fe x −1 Se x /MXene/carbonaceous nanoribbon heterostructure. As a result, the assembled Na/K full cells containing MXene‐supported Fe x −1 Se x @carbonaceous anodes possess stable large‐ion storage capabilities.