Fluorinated Covalent-Organic Framework-Based Quasi-Solid Electrolyte Enable Low-Temperature Lithium-ion Battery

Abstract

Maintaining stable operation over a wide temperature range (−40-110 °C) still constitutes a critical challenge for quasi-solid-state electrolytes (QSSEs), particularly under extreme cold conditions. Here, a series of covalent triazine frameworks have been obtained, in which COF-TA0.5TF0.5 involving multi-component functionalities of C=N linkages, triazine cores, -F atoms and rich channels, will propose a promising solution to this predicament above, realizing a significant improvement in wide-temperature electrochemical performance. Signally, the ionic conductivity of COF-TA0.5TF0.5 QSSE can be maintained up to 10−3 S cm−1 from −40 to 110 °C (1.07×10−3 to 9.11×10−3 S cm−1), and the transference number is as high as 0.91 and 0.87 at room temperature and −40 °C respectively, revealing outstanding prospects for low-temperature applications. Furthermore, COF-TA0.5TF0.5 features excellent cyclic stability and lithium dendrite inhibition capacity with 1600 h long-circulation under 0.1 mA cm−2 and 99.80% coulomb efficiency retention rate after 100 cycles with 0.1 C at −20 °C. Density functional theory (DFT) calculation reveals that COF-TA0.5TF0.5 with rich lithium-philic sites and stronger adsorption binding energy for PF6− are conducive to facilitating lithium salt dissociation and Li+ transport. This work opens a new avenue to broaden the wide-temperature application of COFs-based quasi-solid lithium-ion battery.