Alternating-sequence polymer chain facilitating Li+ transport in covalent organic frameworks

Covalent organic frameworks-based solid-state electrolytes have attracted significant attention in recent years due to their design flexibility, intrinsic porosity, and environmentally friendly characteristics. However, their practical application in batteries remains limited by inadequate ionic conductivity and Li+ transference number, primarily arising from the absence of effective strategies to modulate the pore chemical environment for ion transport. In this study, we introduce a pore-engineering approach by incorporating alternating oxyethylene and perfluoroalkyl chains into the covalent organic frameworks. This sequence-controlled modification simultaneously suppresses anion migration and mitigates lithium-ion aggregation, thereby constructing a continuous and efficient site-to-site Li+ transport pathway. Benefiting from this design, the resulting covalent organic framework exhibits a high Li+ conductivity of 1.06 mS·cm−1 at 25 °C and an Li+ transference number of 0.9. A symmetric Li | |Li cell delivers Li plating/stripping stability over 7500 hours with minimal voltage polarization at 0.2 mA·cm−2 and areal capacity of 0.2 mAh·cm−2. Furthermore, solid-state Li | |LiNi0.8Mn0.1Co0.1O2 battery demonstrates a specific capacity of 180 mAh·g−1 at 1 C (1 C = 200 mA·g−1) and long-term stability at 5 C, retaining 80% capacity after 700 cycles. Here we report pore design strategy and open avenues for the development of high-performance, fast-charging solid-state lithium batteries. Practical use of covalent organic framework-based solid electrolytes is hindered by their mediocre ionic conduction. Here, authors engineer the pore structure via incorporation of alternating oxyethylene and perfluoroalkyl chains, suppressing anion migration and improving Li+ ion transport, achieving 1.06mS·cm-1 at 25 °C and transference number of 0.9.