Flexible and alternant-layered cellulose nanofiber/graphene film with superior thermal conductivity and efficient electromagnetic interference shielding

Inspired by sedimentary rock structure, we demonstrate a flexible heterogeneous multilayered film with high thermal conductivity (TC) and excellent electromagnetic interference (EMI) shielding performance by stacking and concentrating graphene nanosheets (GNS) into alternating conductive layers. Typically, the multilayered film with alternating cellulose nanofiber (CNF) layers and conductive CNF/GNS layers was fabricated by alternating vacuum filtration. Arising from the unique nacre-like oriented structure and highly concentrated conductive filler, high-efficiency phonon and electron transmission paths can be formed in the obtained multilayered CNF@GNS film. As a result, the optimal film with only 25 wt% GNS reveal a high in-plane TC of 33.55 W/(m.K), which increases by 144.6% comparing to the homogeneous CNF/GNS film. Simultaneously, the multilayered films exhibit the effective EMI shielding performance with the highest shielding effectiveness (SE) of 27.4 dB, which is mainly attributed to the enhancing impedance matching and multiple microwave reflections induced by the unique alternating multilayer structure.