Covalent Organic Framework-Derived Quasi-Solid Electrolyte for Low-Temperature Lithium-Ion Battery

Covalent organic frameworks (COFs) are attractive candidates for Li+-conducting electrolytes owing to their regular channels and tailored functionalities. However, most COF electrolytes are employed at high temperatures, challenging their practical use. Herein, tailored COFs coupled with PEG composite electrolytes were designed to construct a flowable network for facilitating Li+ transport at lower temperatures. Benefiting from the interaction between the rigid COF structure and flowing PEG chain, the ionic conductivity of the quasi-solid electrolytes reached 9.74 × 10–7 S cm–1 (−40 °C), 7.10 × 10–5 S cm–1 (0 °C), and 1.36 × 10–3 S cm–1 (80 °C). The resultant LiFePO4|Li cell delivered a discharge specific capacity of 132.5 mAh g–1 after 80 cycles at 10 °C. The Li–Li symmetrical cell displayed a long-time operation stability of over 800 h when cycled at a low temperature (10 °C). This work opens a new avenue to broaden the practical application of COFs electrolytes in quasi-solid lithium-ion batteries.