Thermally rearranged covalent organic framework with flame-retardancy as a high safety Li-ion solid electrolyte

• DOI: 10.1016/j.esci.2022.03.004
• Publication Date: 2022-03-14T21:48:32Z
• Authors: Zhifang Wang; Yushu Zhang; Penghui Zhang; Dong Yan; Jinjin Liu; Yao Chen; Qi Liu; Peng Cheng; Michael J. Zaworotko; Zhenjie Zhang
• Keywords: Covalent organic framework

Solid polymer electrolytes have demonstrated high promise to solve the safety problems caused by conventional liquid in lithium ion batteries. However, inherent flammability of most electrolyte materials remains unresolved, hence hindering their further industrial application. Addressing this challenge, we designed and constructed a thermal-responsive imide-linked covalent organic framework (COF) bearing ortho-positioned hydroxy groups as precursors, which can conduct thermal rearrangement transform into highly crystalline robust benzoxazole-linked COF upon heating. Benefiting from release carbon dioxide through reaction, platform exhibited excellent flame retardant properties. By contrast, classic COFs (e.g., boronate ester, imine, olefin, imide linked) were all flammable. Moreover, incorporating polyethylene glycol Li salt channels produce solid with outstanding retardancy, ionic conductivity (6.42 ​× ​10−4 ​S ​cm−1) lithium-ion transference number 0.95. This strategy not only opens new route for fabrication ultrastable COFs, but also provides promising perspectives designing flame-retardant energy-related applications.