Advancements in power electronics necessitate dielectric polymer films capable of operating at high temperatures and possessing high energy density. Although significant strides have been achieved by integrating inorganic fillers into high-temperature polymer matrices, the inherently low dielectric constants of these matrices have tempered the magnitude of success. In this work, we report an innovative nanocomposite based on sulfonylated polyimide (SPI), distinguished by the incorporation of sulfonyl groups within the SPI backbone and the inclusion of wide bandgap hafnium dioxide (HfO₂) nanofillers. The nanocomposite has demonstrated notable enhancements in thermal stability, dielectric properties, and capacitive performance at elevated temperatures. Detailed simulations at both molecular and mesoscopic levels have elucidated the mechanisms behind these improvements, which could be attributed to confined segmental motion, an optimized electronic band structure, and a diminished incidence of dielectric breakdown ascribed to the presence of sulfonyl groups. Remarkably, the SPI-HfO₂ nanocomposite demonstrates a high charge-discharge efficiency of 95.7% at an elevated temperature of 150 °C and an applied electric field of 200 MV/m. Furthermore, it achieves a maximum discharged energy density of 2.71 J/cm³, signalling its substantial potential for energy storage applications under extreme conditions.

To achieve excellent electromagnetic wave (EMW) absorption properties, the microstructure design of the absorber is critical. In this work, six kinds of N-Ni/C nanostructures with different morphologies were prepared by one-step hydrothermal method and high temperature carbonization by adjusting the types of nickel salts and reaction solvents. The EMW absorption performance of six different morphologies of N-Ni/C nanostructures was compared and analyzed. Among them, it is found that the nanoflower-like N-Ni/C composite has excellent dielectric loss and magnetic loss synergistic effect due to its polycrystalline structure, and can obtain excellent EMW absorption performance. The minimum reflection loss value at a thickness of 1.9 mm is −59.56 dB at 16.88 GHz, and the effective absorption bandwidth value reaches 6.0 GHz at a thickness of 2.2 mm. Our research shows that different morphologies and multiple lattice structures of nanostructures with the same composition have a significant influence on EMW absorption performance, which provides new research ideas for developing high-performance EMW absorbing materials.

Two-dimensional metal carbide or nitride materials (MXenes) are widely used in electromagnetic wave absorption because of their unique structure. Herein, a novel composite preparation strategy has been proposed to design dendritic nanofibers based on the electrostatic spinning methods. The multifunctional MXene nanosheets are used as the dendritic matrix, and magnetic nanoparticles are embedded in the nanosheets as magnetic loss units. Multidimensional nanocomposites have interlaced carbon fiber networks, large-scale magnetically coupled networks, and a lot of multi-heterojunction interface structures, which endow the composites with extraordinary conduction loss, magnetic loss, and polarization loss capabilities, respectively. The impedance matching and loss mechanisms of the composites are improved by optimizing the synergistic relationship between the components and building a suitable structure. The optimum reflection loss (RL) of −54.1 dB is achieved at 2.7 mm and a wide effective absorption bandwidth (EAB, RL below −10 dB) of 7.76 GHz is obtained at a small thickness of 2.1 mm for the nanocomposites. The distinctive microstructures of the nanofibrous membranes give rise to their flexibility, waterproof, and electromagnetic wave absorption performance and endow the nanofibrous membranes potential to be utilized as lightweight, efficient electromagnetic wave protective fabric in harsh environment.