Interfacial and Electronic Modulation via Localized Sulfurization for Boosting Lithium Storage Kinetics

Abstract Structural modulation endows electrochemical hybrids with promising energy storage properties owing to their adjustable interfacial and/or electronic characteristics. For MXene‐based materials, however, the facile but effective strategies for tuning their structural properties at nanoscale are still lacking. Herein, 3D crumpled S‐functionalized Ti₃C₂T_x substrate is rationally integrated with Fe₃O₄/FeS heterostructures via coprecipitation and subsequent partial sulfurization to induce a highly active and stable electrode architecture. The unique heterostructures with tuned electronic properties can induce improved kinetics and structural stability. The surface engineering by S terminations on the MXene further unlocks extra (pseudo)capacitive lithium storage. Serving as anode for lithium storage, the optimized electrode delivers an excellent long‐term cycling stability (913.9 mAh g⁻¹ after 1000 cycles at 1 A g⁻¹) and superior rate capability (490.4 mAh g⁻¹ at 10 A g⁻¹). Moreover, the (de)lithiation pathways associated with energy storage mechanisms are further revealed by operando X‐ray diffraction, in situ electroanalytical techniques, and first‐principles calculations. The hybrid electrode is proved to undergo stepwise phase transformations during discharging but a relatively uniform reconversion during charging, suggesting an asymmetric conversion mechanism. This work provides a novel strategy for designing high‐performance hybrids and paves the way for in‐depth understanding of complex lithium intercalation and conversion reactions.