Toward Overcoming the Strength‐Toughness Trade‐off in Cellulose Bulk Material by Tuning the Double‐Network Structure With Hierarchical Hydrogen Bonding

Overcoming the conflict between strength and toughness in polymer‐matrix composites without chemically cross‐linked networks remains challenging. Herein, we report an all‐cellulose bioplastic (AC‐bioplastic) with excellent strength and toughness via a hierarchical hydrogen‐bonding double‐network (DN) structure. Natural wood fibers are delignified to cellulose microfibers, which cross‐link with regenerated cellulose nanofibers formed using LiCl/DMAc solvent, creating an interpenetrating DN network. The strong hydrogen bonds (H‐bonds) between micro/nano‐cellulose networks provide primary mechanical strength for AC‐bioplastic, while the weak H‐bonds formed by the interaction between Cl − and cellulose nanofibers contribute to the slipping and deformation behaviors. As a result, the AC‐bioplastic exhibits a tensile strength of 95.8 MPa and a toughness of 84.8 MJ m −3 , surpassing many representative cellulose‐based materials while remaining comparable to state‐of‐the‐art polymeric elastomers. Notably, the thickened AC‐bioplastic bulk achieves a compression strength of 200 MPa under a high strain rate of 4000 s −1 , outperforming typical impact‐resistant materials including PC and ABS. Importantly, this approach avoids complete cellulose nanofibril dissociation, enabling the facile and scalable manufacturing. Combined with its intrinsic thermal stability and recyclability, the AC‐bioplastic provides a promising lightweight and renewable alternative for sustainable structural materials.