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In order to ensure the operational reliability and information security of sophisticated electronic components and to protect human health, efficient electromagnetic interference (EMI) shielding materials are required to attenuate electromagnetic wave energy. In this work, the cellulose solution is obtained by dissolving cotton through hydrogen bond driving self-assembly using sodium hydroxide (NaOH)/urea solution, and cellulose aerogels (CA) are prepared by gelation and freeze-drying. Then, the cellulose carbon aerogel@reduced graphene oxide aerogels (CCA@rGO) are prepared by vacuum impregnation, freeze-drying followed by thermal annealing, and finally, the CCA@rGO/polydimethylsiloxane (PDMS) EMI shielding composites are prepared by backfilling with PDMS. Owing to skin-core structure of CCA@rGO, the complete three-dimensional (3D) double-layer conductive network can be successfully constructed. When the loading of CCA@rGO is 3.05 wt%, CCA@rGO/PDMS EMI shielding composites have an excellent EMI shielding effectiveness (EMI SE) of 51 dB, which is 3.9 times higher than that of the co-blended CCA/rGO/PDMS EMI shielding composites (13 dB) with the same loading of fillers. At this time, the CCA@rGO/PDMS EMI shielding composites have excellent thermal stability (THRI of 178.3 °C) and good thermal conductivity coefficient (λ of 0.65 W m-1 K-1). Excellent comprehensive performance makes CCA@rGO/PDMS EMI shielding composites great prospect for applications in lightweight, flexible EMI shielding composites. Graphic abstract

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Significantly improved thermal conductivities and a more accurate thermal conductivity model were achieved.

shielding materials can effectively protect flexible electronic devices and the environment where they are located, prevent electromagnetic information leakage, cut off electromagnetic wave propagation, and suppress electromagnetic wave radiation and interference. [2] With the new development trend for intelligent, portable, and wearable flexible electronic devices, higher requirements are also put forward for the flexibility, lightweight, thermal conductivities, and mechanical properties of EMI shielding materials. Therefore, there is an urgent need to fabricate novel kinds of multi-functional flexible EMI shielding composite films with high-performances. [3] Recent years, polymer-based EMI shielding composites have gradually replaced traditional metal EMI shielding materials due to their advantages of lightweight, corrosion resistance, and easy processing. [4] Polymer-based EMI shielding composites are composed of polymer matrix, magnetic nanoparticles (iron carbonyl, nickel carbonyl, and ferroferric oxide (Fe 3 O 4 ), etc.), and/or electrically conductive fillers (graphite, carbon nanotubes, graphene, etc.). [5] Fe 3 O 4 nanoparticles are strong in magnetism, and possess excellent magnetic loss performances for electromagnetic waves, having been widely used as the electromagnetic wave absorbers for polymer-based EMI shielding composites. [6] However, the electrical conductivity performances of magnetic Fe 3 O 4 nanoparticles are relatively poor, which easily leads to damage to the electrical conductivity loss of the polymer-based EMI shielding composites. In most cases, they need to be combined with electrically conductive fillers to achieve better EMI shielding performances through electromagnetic coordination. [7] MXenes are 2D materials with excellent electrical conductivity (σ) and surface activity, and have received extensive attention from researchers in recent years. [8] Ti 3 C 2 T x , as the typical representative, possesses better σ, stability, and film-forming property than other MXenes, and can be used as the electrically conductive fillers to fabricate EMI shielding composite films with high-performances. [9] Researchers generally prepare polymer-based EMI shielding composite films by blending fillers and polymer matrix. [10] However, the simply blending method has certain limitations. With the rapid development and popularization of smart, portable, and wearable flexible electronic devices, urgent demands have been raised for flexible electromagnetic interference (EMI) shielding films to solve related electromagnetic pollution problems. With polyvinyl alcohol (PVA) as polymer matrix, the sandwich-structured EMI shielding nanocomposite films are prepared via electrospinning-laying-hot pressing technology, where Fe 3 O 4 / PVA composite electrospun nanofibers in the top and bottom layers and Ti 3 C 2 T x /PVA composite electrospun nanofibers in the middle layer. Owing to the electrospinning process and the successful construction of the sandwich structure, when the amounts of Ti 3 C 2 T x an...