C₆₀-Mediated d-π Conjugation Induces Electronic Reconstruction to Boost Charge Storage of Nb₂C/Nb₂O₅ Heterostructure...

Regulating orbital electronic structure to enhance the charge-storage capability of anode materials is critical for developing high-performance lithium-ion hybrid capacitors (LIHCs). Herein, we report a novel interfacial engineering strategy that employs fullerene C₆₀-mediated d-π conjugation within a Nb₂C/Nb₂O₅ heterostructure (denoted as C₆₀-Nb₂C/Nb₂O₅) to realize simultaneous electronic reconstruction and structural optimization. The introduced C₆₀ forms robust d-π conjugation with the d-orbitals of Nb, acting as an electron acceptor to drive directional charge transfer across both the C₆₀/Nb₂C and Nb₂C/Nb₂O₅ interfaces. Combined theoretical and experimental analyses confirm that orbital engineering between Nb (d_xy/d_yz) and C₆₀ (p) facilitates electron backflow, improves intrinsic electronic conductivity, substantially lowers the Li⁺ adsorption barrier, triggers an upward shift of the d-band center, and accelerates electron-transfer kinetics. Consequently, the C₆₀-Nb₂C/Nb₂O₅ anode delivers a remarkable reversible capacity of 658.8 mAh g-¹ at 0.1 A g-¹ and excellent rate capability. The assembled C₆₀-Nb₂C/Nb₂O₅//activated carbon LIHC achieves a high energy density of 199.5 Wh kg-¹, ranking among the highest values reported for MXene-based LIHCs. This work elucidates a molecular-mediated interfacial electronic engineering mechanism for tailoring charge-storage behavior, providing a rational design strategy for advanced electrochemical energy-storage systems.