All‐Natural Self‐Bonded Biocomposite Providing Superior Electromagnetic Interference Shield Performance with Effective Absorption

Abstract The development of electronics and telecommunication technologies requires high‐performance electromagnetic interference (EMI) shielding materials to mitigate the rising concern of electromagnetic pollution. In this work, a novel partial dissolution approach is reported to fabricate an all‐natural eco‐friendly high‐strength cellulose/biochar (Cel@BC) composite showing excellent EMI shielding performance due to its densely crosslinking conductive core–shell structure. This results in a high conductivity of 130.9 S m −1 , providing ultra‐high metal‐level EMI shielding effectiveness ≈72.4 dB. Absorption effectiveness reaches a maximum of 68.2 dB with electromagnetic waves absorbance >40%, featuring an obvious advantage over traditional reflecting‐dominated metals. This Cel@BC biocomposite presents lower environmental impacts than existing metals and petrochemical‐based plastics, as it biodegrades into carbon‐sequestering biochar. These outstanding EMI shielding properties and advantageous eco‐friendly nature make it an excellent cost‐efficient alternative to existing shielding materials on the market.