Engineering Covalent and Noncovalent Interface Synergy in MXenes for Ultralong-life and Efficient Energy Storage.

MXenes serve as pivotal candidates for pseudocapacitive energy storage owing to sound proton/electron-transport capability and tunable topology. However, the metastable surface terminal properties and the progressive oxidation leads to drastic capacity fading, posing significant challenges for sustainable energy applications. Here, with the aramid nanofiber as the interface mediator, we engineer the thermal reconstruction of MXenes to synergistically introduce interfacial covalent and noncovalent interactions, resulting in a high specific capacitance of 531.9 F g and a capacity retention of 92.2% after 180, 000 cycles. In-situ heating transmission electron microscopy observations demonstrate the formation of ultrafine mesopores with interfacial reconstitution for mass transport intensification. Theoretical calculations indicate electronic accumulation adjacent to the covalent bonds, endowing the heterogeneous interface with fast electronic conduction capability and favorable adsorption of H. In addition, the dual modification improves the oxidation energy barrier of MXenes to TiO, resulting in a thermodynamically promoted and sustainable storage microenvironment. Our research emphasizes the synergistic mechanism of noncovalent interactions and covalent bonding toward an optimal reaction interface, which breaks the trade-off of MXenes between the reactivity and stability for energetic energy storage.