Electromagnetic wave (EM) absorption materials with broader effective absorption bandwidth (EAB), lightweight, and thinness characteristics are highly desirable in areas of wearable device and portable electronics. However, there are still many obstacles to simultaneously satisfy the above critical requirements required by new high-performance EM absorption materials. Herein, for the first time, Ti 3 C 2 T X MXenes are selected as the dielectric mediator to prepare reduced graphene oxide (RGO)/Ti 3 C 2 T X hybrids foam with hollow core-shell architectures and controllable complex permittivity via self-assembly and sacrificial template processes, under the guidance of theoretical calculations. RGO is grafted flatly on the outer surface of the Ti 3 C 2 T X spheres-core, forming a unique heterostructure. The RGO/Ti 3 C 2 T X foam possesses excellent EM absorption performance superior to all reported foam-based counterparts, the EAB covers the whole X-band at 3.2 mm while the density is merely 0.0033 g cm −3 , and its specific EM absorption performance (SMAP = RL (dB)/Thickness (cm)/Density (g cm −3 )) value exceeds 14 299.2 dB cm −2 g −1 , verifying the above theoretical results. This study is expected to guide future exploration on designing high-performance EM absorption materials, and the RGO/Ti 3 C 2 T X foam can be promising candidates in energy storage, sensors, and wearable electronics fields.

Lightweight absorption-dominated electromagnetic interference (EMI) shielding materials are more attractive than conventional reflection-dominated counterparts because they minimize the twice pollution of the reflected electromagnetic (EM) wave. Here, porous Ti2CT x MXene/poly­(vinyl alcohol) composite foams constructed by few-layered Ti2CT x (f-Ti2CT x ) MXene and poly­(vinyl alcohol) (PVA) are fabricated via a facile freeze-drying method. As superior EMI shielding materials, their calculated specific shielding effectiveness reaches up to 5136 dB cm2 g–1 with an ultralow filler content of only 0.15 vol % and reflection effectiveness (SER) of less than 2 dB, representing the excellent absorption-dominated shielding performance. Contrast experiment reveals that the good impedance matching derived from the multiple porous structures, internal reflection, and polarization effect (dipole and interfacial polarization) plays a synergistic role in the improved absorption efficiency and superior EMI shielding performance. Consequently, this work provides a promising MXene-based EMI shielding candidate with lightweight and high strength features.

In this work, mesoporous carbon hollow microspheres (PCHMs) with designable mesoporous shell and interior void are constructed by a facile in situ stöber templating approach and a pyrolysis-etching process. The PCHMs are characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, Raman spectroscopy, and nitrogen adsorption and desorption system. A uniform mesoporous shell (pore size 4.7 nm) with a thickness of 55 nm and a cavity size of 345 nm is realized. The composite of paraffin mixed with 20 wt % PCHMs exhibits a minimum reflection coefficient (RC) of -84 dB at 8.2 GHz with a sample thickness of 3.9 mm and an effective absorption bandwidth (EAB) of 4.8 GHz below -10 dB (>90% electromagnetic wave is attenuated). Moreover, the composite of phenolic resin mixed with 20 wt % PCHMs exhibits an ultrawide EAB of 8 GHz below -10 dB with a thinner thickness of 2.15 mm. Such excellent electromagnetic wave absorption properties are ascribed to the large carbon-air interface in the mesoporous shell and interior void, which is favorable for the matching of characteristic impedance as compared with carbon hollow microspheres and carbon solid microspheres. Considering the excellent performance of PCHMs, we believe the as-fabricated PCHMs can be promising candidates as highly effective microwave absorbers, and the design philosophy can be extended to other spherical absorbers.

Nonbattery behavior related phase transition of electrodes is usually not favorable for any batteries because it results in performance degradation at all times. Here, we demonstrate a zinc hybrid-ion battery (ZHIB) with an unusual capacity enhancement even within 18 000 cycles by employing V2CTX MXene as the cathode, enormously differing from all reported counterparts with capacity degradation initiated within hundreds of cycles. The dominated mechanisms are determined to be MXene delamination and an unexpected phase transition during cycling. Both the original cathode and secondary derivative contribute to capacity simultaneously, resulting in the unusual capacity enhancement. Consequently, the specific capacity of 508 mAh g–1 (highest for all reported aqueous zinc-ion batteries) and high energy density of 386.2 Wh kg–1 are realized. Also, the quasi-solid-state batteries fabricated can output stably at −20 °C and in bending, twisting, stabbing, and cutting conditions. Our work brings an effective approach, that is, utilizing “unstable” electrode materials, which should usually be avoided, to achieve continuously enhanced performance of a battery. The idea to use both original and secondary materials for energy storage may be developed to be a general method to achieve extraordinary cycling stability of batteries.

Ti3C2TxMXenes modified within situgrown carbon nanotubes (CNTs) are fabricatedviaa simple catalytic chemical vapor deposition (CVD) process.