Modulating Electrochemical Energy Storage and Multi‐Spectra Defense of MXenes by Interfacial Dual‐Filler Engineering

Abstract MXenes have attracted growing interest in electrochemical energy storage owing to their high electronic conductivity and editable surface chemistry. Besides, rendering MXenes with spectrum defense properties further broadens their versatile applications. However, the development of MXenes suffers from weak van der Waal interaction‐driven self‐restacking that leads to random alignment and inferior interface microenvironments. Herein, a nacre‐inspired MXene film is tailored by dual‐filling of 2‐ureido‐4[1H]‐pyrimidinone (UPy)‐modified polyvinyl alcohol (PVA‐UPy) and carbon nanotubes (CNTs). The dual‐nanofillers engineering endows the nanocomposite film with a highly ordered structure (a Herman's order value of 0.838), a high mechanical strength (139.5 MPa), and continuous conductive pathways of both the ab plane and c ‐axis. As a proof‐of‐concept, the tailored nanocomposite film achieves a considerable capacitance of 508.2 F cm ⁻³ and long‐term cycling stability without performance degradation for 10 000 cycles. It is efficient for spectra defense in radar and infrared bands, displaying a high electromagnetic shielding capacity (19186 dB cm ² g ⁻¹ ) and a super‐low infrared (IR) emissivity (0.16), with negligible performance decay after saving in the air for 1 year, responsible for the applications in specific and complex conditions. This interfacial dual‐filler engineering concept showcases effective nanotechnology toward sustainable energy applications with a long lifetime and safety.