Novel Cellulosic Fiber Composites with Integrated Multi-Band Electromagnetic Interference Shielding and Energy Storage Functionalities

• A mild TEMPO-mediated oxidation system introduces abundant macropores into cellulose fiber skeleton, enhancing reactivity and providing active sites for energy storage. • The composite achieves exceptional multi-band EMI shielding efficiency exceeding 99.99% (>100 dB) across L, S, C, and X bands. • Integrated energy storage performance includes high areal capacitance (12.44 F cm−2) and energy density (3.99 mWh cm−2) with 90.23% capacitance retention after 10,000 cycles. • This work demonstrates a sustainable strategy for developing bio-based multifunctional materials for EMI shielding and energy storage applications.