An asymmetric sandwich structural cellulose-based film with self-supported MXene and AgNW layers for flexible electromagnetic interference shielding and thermal management

Abstract

Flexible cellulose-based conductive films reveal high potential in electromagnetic interference (EMI) shielding and thermal management applications. However, the high contact electrical/thermal resistance in these films is still a challenge to face. In this work, an asymmetric sandwich structural film containing a cellulose nanofiber (CNF) skin-layer and self-supported Ti₃C₂T_x MXene and silver nanowire (AgNW) core-layers (CNF@MXene@AgNW film) was fabricated through layer-by-layer assembled vacuum-assisted filtration. The unique sandwich structure not only provides a highly conductive network by the highly oriented and self-supported conductive core-layers, but also maintains its structural integrity by ambilateral CNF layers. As a result, the CNF@MXene@AgNW film reveals a strong tensile strength of 118 MPa and a toughness of 4.75 MJ m⁻³, super-flexibility (minimum bending radius of ∼85 μm), a high electrical conductivity (37 378.2 S m⁻¹), effective EMI shield effectiveness (SE, 55.9 dB), outstanding specific SE (SSE/t, 10 647.6 dB cm² g⁻¹) and high in-plane thermal conductivity (15.53 W m⁻¹ K⁻¹), simultaneously. More interestingly, the sandwich film also reveals outstanding solar-thermal energy conversion ability, which guarantees its normal function in extremely cold environment. The unique asymmetric sandwich structure provides a new strategy for designing and preparing high-performance EMI shielding and thermal conductive films.