Flexible and conductive MXene films and nanocomposites with high capacitance

MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti₃C₂T_x MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti₃C₂T_x/ polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 10⁴ S/m in the case of the Ti₃C₂T_x/PVA composite film and 2.4 × 10⁵ S/m for pure Ti₃C₂T_x films. The tensile strength of the Ti₃C₂T_x/PVA composites was significantly enhanced compared with pure Ti₃C₂T_x or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ~530 F/cm³ for MXene/PVA-KOH composite film at 2 mV/s. To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few.