Tailoring interfacial dipole of MXene for enabling wide-range temperature lithium-ion capacitors

The synergistic triple dipole constructs a dipole electric field in G(H + )-MXene. • G(H + )-MXene exhibits outstanding Li storage capacity and temperature adaptability. • The flexible G(H + )-MXene//AC pouch cell retains 87.1% capacity after 10,000 cycles. Lithium-ion capacitors (LICs) often suffer from kinetic mismatch between capacitive cathodes and battery-type anodes, limiting their wide-range temperature applicability. Herein, we propose an interfacial dipole engineering strategy to address this challenge by modifying Ti 3 C 2 T x MXene with protonated guanine (G(H + )) to yield G(H + )-MXene. Density functional theory (DFT) calculations reveal that the energy difference between the charge neutrality level (E CNL ) of G(H + ) and the Fermi level (E f ) of Ti 3 C 2 T x can drive directional interfacial charge redistribution. The resulting charge-transfer dipole between Ti 3 C 2 T x and G(H + ) couples with the intrinsic molecular dipole of G(H + ), the surface dipole of MXene, and the dipole induced by newly formed Ti N bonds. This synergy generates a robust interfacial dipole electric field that significantly accelerates Li + transport and lowers the associated energy barrier. Consequently, the assembled G(H + )-MXene//activated carbon LIC delivers high energy and power densities, exhibits impressive wide-temperature operability (from 40 to −40 °C), and maintains remarkable flexibility even when bent to 180°. This work provides a promising strategy for tailoring the interfacial structure of MXenes to overcome performance bottlenecks in wide-temperature energy storage systems. Download: Download high-res image (160KB) Download: Download full-size image