Durable and sustainable CoFe2O4@MXene-silver nanowires/cellulose nanofibers composite films with controllable electric-magnetic gradient towards high-efficiency electromagnetic interference shielding and Joule heating capacity

Exploring electromagnetic waves (EMW) absorption-dominated high-performance electromagnetic interference (EMI) shielding materials with robust mechanical properties and remarkable Joule heating capability is highly desired but remains a daunting challenge for the development of modern electronic equipment. Herein, durable and multifunctional cellulose nanofiber-based composite films with elaborate electric-magnetic dual gradient structure were successfully fabricated through highly controllable vacuum-assisted filtration technology. The electric-magnetic dual gradient network consists of CoFe2O4@MXene hybrids with electric-magnetic cooperative loss concentrated on the top region as impedance matching layer and silver nanowires (AgNWs) with high conductivity placed on the bottom as high-efficiency shielding layer. Benefiting from the construction of dual gradient network with rational arrangement of the impedance matching layer and conductive shielding layer, the synergy of electric-magnetic loss, polarization loss induced by the numerous heterointerfaces and "absorptionreflection-reabsorption" shielding mechanism, the resultant composite films simultaneously reveal ultraefficient EMI shielding effectiveness (SE) and low EMW reflectivity. The prepared composite films (0.1 mm in thickness) achieve an extraordinary EMI SE of 84.3 dB and a satisfactory reflection coefficient of 0.42, realizing EMW absorption-dominated shielding feature. Moreover, the mechanical properties and Joule heating capacity of the prepared composite films are outstanding, which mainly benefits from the construction of hierarchically layered structure. This work paves a novel route for designing and fabricating absorption-dominated high-performance EMI shielding composite films with durable mechanical performance and outstanding Joule heating capability, which are potentially suitable for new-generation advanced electronics.