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[Display omitted] • A novel strategy was proposed to achieve flexible liquid metal/cellulose nanofiber film. • The film exhibits excellent structural stability and EMI shielding effectiveness of ~ 65 dB. • Simulation in the frequency domain was introduced to investigate the shielding mechanism. Liquid metal (LM) is a promising candidate for electromagnetic interference (EMI) shielding due to the superb electrical conductivity and easy processing. However, poor compatibility caused by high surface tension, insulated oxide shells formed during processing, and unmanageable fluidity at elevated temperature of LM severely hinder its application in the field of EMI shielding. Herein, we develop a novel processing strategy integrating ball-milling dispersion, freeze-drying and compression molding to achieve free-standing and flexible LM/cellulose nanofiber composites (LM/CNF) film, in which the oxide shells of LM droplets generated by ball-milling are broken by mechanical compression, and LM droplets are coalesced while confined by CNF to construct a continuously conductive path. As a result, the robust LM/CNF film shows tensile strength of above 30 MPa, and it possesses electrical conductivity of 96,000 S/m, leading to remarkable shielding effectiveness (SE) of above 65 dB with a thickness of only 300 µm in a broad frequency range of 4–18 GHz covering C-band, X-band and Ku-band. Moreover, LM/CNF film exhibits excellent structural stability and EMI shielding performance reliability after high-temperature treatment. Besides, simulation in the frequency domain with ANSYS HFSS 2019 R2 is performed to intuitively understand the shielding mechanism of LM/CNF film. It is found that the attenuation of electromagnetic waves is mainly based on reflection. This study proposes a fresh scenario to achieve high-performance EMI shielding material and paves the way for potential applications of LM in portable and wearable smart electronics. [ABSTRACT FROM AUTHOR]

• A new strategy is developed to achieve chemically stable Ti 3 C 2 T x MXene. • Mechanical properties of IL-MXene film is significantly improved. • The mechanism for improved chemical stability of IL-MXene sheet is proposed. Ti 3 C 2 T x MXene with two-dimensional (2D)-layered structure shows potential application in various fields owing to its superb metallic conductivity and excellent solution processability. However, a fundamental challenge limiting the implementation of Ti 3 C 2 T x in practical applications is its susceptibility to oxidation in either humid or aqueous environments only within a few days, which results in the disassembly of the 2D-layered structure and severely deteriorates the functional properties including electrical conductivity, mechanical strength and EMI shielding performance. Herein, we firstly demonstrate a robust procedure to protect sensitive Ti 3 C 2 T x from degradation by modification with imidazolium-based inion liquid (IL), which remarkably improves the chemical stability of Ti 3 C 2 T x in aqueous and significantly increases the mechanical strength of assembled freestanding Ti 3 C 2 T x film (IL-MXene). The crystalline structure of IL-MXene sheet remains intact up to 30 days and preserves the 2D-layered structure as long as 8 months in aqueous, meanwhile, the tensile strength of freestanding IL-MXene film is as high as 75.9 ± 4.9 MPa and the increment is up to 84% when compared to that of untreated MXene film (41.2 ± 4.5 MPa). A novel mechanism for improved chemical stability of MXene sheet was proposed and elucidated based on the radical-scavenging ability of IL and the surface chemistry of MXene sheet. This study provides a new strategy to achieve chemically stable Ti 3 C 2 T x and improved mechanical strength of assembled MXene film, which is also available for other type of MXenes. [ABSTRACT FROM AUTHOR]