Bipolar fluorinated covalent triazine framework cathode with high lithium storage and long cycling capability.

Abstract

Organic materials with adjustable structures and wide sources are expected to become potential candidates for commercial cathodes of lithium-ion batteries (LIBs). However, most organic materials have unstable structures, poor conductivity, and are easily soluble in electrolytes, resulting in unsatisfactory lithium storage performance. Covalent–organic frameworks have attracted extensive attention due to their stable frame structures, adjustable pore structures and functionalized official groups. Herein, a fluorinated covalent triazine framework (FCTF) is synthesized by a simple ion-thermal method. Compared with the fluorine-free covalent triazine frameworks (CTFs), the introduction of fluorine improves the lithium storage performance of CTF. When used as a cathode for lithium ion batteries, FCTF can retain a reversible capacity of 125.6 mA h g−1 after 200 cycles at a current density of 100 mA g−1. Besides, it also delivers 106.3 mA h g−1 after 400 cycles at a current density of 200 mA g−1 with 0.03% decrease per cycle (from 40 to 400 cycles).