Cellulose Fiber‐Engineered Gradient Interfacial Channels as Ion‐Highways for High‐Loading, Long‐Life Lithium‐Ion Batteries

Developing thick electrodes with high active material content is crucial to achieving high‐energy‐density lithium‐ion batteries; yet it remains challenging due to the conflicting requirements of mechanical integrity and rapid ion transport. Here, we propose a scalable papermaking strategy to address this dilemma by constructing a minimal mass fraction (~3 wt%) of cellulose fibers into a three‐dimensional scaffold. This scaffold not only ensures the mechanical robustness of electrodes with ultra‐high active material content (96 wt%) but, more importantly, creates well‐defined gradient interfacial channels. These channels function as efficient “ion highways,” which significantly enhance electrolyte wettability and minimize ion‐diffusion resistance. When paired in a full cell (lithium manganese iron phosphate//lithium titanate), this design enables exceptional cycling stability and rate capability, maintaining 95.3% capacity after 500 cycles at 0.5 C and 72.3% over 1000 cycles at 2 C, substantially outperforming conventional counterparts. Post‐cycling analysis reveals that performance degradation primarily stems from the active materials, while the cellulose framework exhibits excellent electrochemical inertness and interfacial stability. This work provides a practical and sustainable paradigm for engineering efficient ion transport pathways, breaking the coupling constraints between mechanics and ionics in high‐loading electrodes.