Covalent Organic Framework Electrolytes for Solid‐State Lithium Batteries: Designing Ion Highways for Next‐Generation Energy Storage

Covalent organic frameworks (COFs) are emerging as a programmable platform for solid electrolytes in solid‐state lithium batteries, since their crystalline, periodically ordered nanochannels can be engineered to enable directional ion transport. These low‐resistance pathways promote directional lithium‐ion (Li + ) migration through a narrower, more spatially ordered distribution of coordination environments, achieved via site‐to‐site hopping and/or guest‐assisted vehicular motion within the channels. This review presents a design‐oriented framework linking COF structural descriptors to ion‐transport metrics through a cause‐effect‐performance relationship. We first summarize the Li + transport mechanism in confined COF channels, covering site‐to‐site hopping along pore walls and guest‐assisted vehicular motion in filled channels. We then correlate (i) topology and channel architecture, (ii) pore‐wall chemical functionality and framework charge, (iii) crystallinity, stacking registry, and channel alignment, and (iv) hybrid COF architectures with performance indicators including ionic conductivity (σ), activation energy (Ea), lithium‐ion transference number (tLi + ), transport anisotropy, and effective conductivity in working membranes (σeff). Through representative case studies, we highlight cases where high intrinsic channel transport does and does not translate into device‐relevant σeff. Finally, we propose standardized reporting practices and device‐level benchmarks to accelerate the shift from empirical materials discovery toward predictive ion‐highway engineering for next‐generation solid‐state lithium batteries.