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

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 (dxy/dyz) 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.