Rational design of polymer electrolytes with three-dimensional cyclodextrin-based covalent organic framework for lithium-iodine batteries

Solid-state electrolytes have great potential due to their unique benefits, such as preventing electrolyte leakage, inhibiting the growth of Li dendrites, and maintaining high safety levels. Nevertheless, a significant challenge is their low ionic conductivity, which persists as a problem for such electrolytes. In this study, a three-dimensional cyclodextrin-based covalent organic framework (CD-Si) was synthesized to address above issue. β-Cyclodextrin (β-CD) was used as a flexible backbone and silicon tetrachloride served as a linker. A polymer electrolyte, PEO/PVDF/CD-Si, was developed and implemented in solid-state LiI2 batteries, in which PEO and PVDF were acted as the matrix and the open-frame CD-Si network as the anchoring medium. The CD-Si can reduce Li+ diffusion energy barriers and accelerate Li+ transport, achieving a high lithium-ion conductivity of 2.4 × 10−3 S cm−1 for PEO/PVDF/CD-Si at room temperature. Furthermore, the assembled symmetric battery achieved an ultra-long cycle life of 10,000 h at a current density of 0.1 mA cm−2.