Flexible and mechanically strong MXene/cellulose-lamellae sheets for electromagnetic interference shielding

•Demonstrated a densification strategy for mechanically strong MXene sheets.•Elimination of voids imparts MXCS with powerful strength and toughness.•The high electrical conductivity induced ultrahigh weight-normalized shielding efficiency.•Hydrogen bonding of UCL induced enhance interlaminar interaction of compact platelet. MXene, two-dimensional layered transition metal carbides, nitride, or carbonitrides, have shown promise for ultrahigh electromagnetic interference (EMI) shielding in flexible electronics and aerospace due to their intrinsic metallic conductivity and mechanical strength. However, weak interfacial interactions, void microstructure defects, and oxidative degradation can leave MXene sheets in a thermodynamically metastable state, resulting in poor EMI shielding and mechanical strength. Herein, we utilized abundant hydrogen-bonded ultrafine cellulose lamella (UCL) to sequentially bridging induced densification of MXene nanosheets. This resulted in improved the tensile strength, toughness, oxidative stability, resistance to ultrasonic decomposition, and super-foldable conductivity of MXene sheets. The resulting MXene@UCL sheets (MXCS) exhibited high electrical conductivity of up to 7649 S cm−1 and ultrahigh weight-normalized shielding efficiency (SSE/t, 53003.45 dB∙cm2 g−1), making them mechanically strong and highly conductive. The MXCS material has a tensile modulus of up to 10.9 ± 0.7 GPa and provides excellent weight-normalized shielding efficiency. Simultaneously, it is capable of enduring 100,000 repetitions of folding without experiencing any damage to its construction or fluctuations in conductivity. Furthermore, high-strength scalable MXCS sheets can be produced using doctor blade casting, commercial resin bonding, and aerogel calendering methods, without compromising their performance. This has significant scientific and practical application potential.