Synthesis of biphenyl-linked covalent triazine frameworks with excellent lithium storage performance as anode in lithium ion battery

Covalent triazine frameworks (CTFs) with rigid triazine linkages and rich molecular pores are viewed as the promising electrode materials, which have the great possibility to tackle the issues including poor structural stability, sluggish ion/electron diffusion and low capacity of conventional organics. In this study, the biphenyl-based CTFs (CTF-2) has been synthesized and proposed as lithium storage material for the first time. Notably, a superlithiation performance is achieved in CTF-2 with almost 4.4 Li+ storage in each aromatic ring (benzene or triazine ring), delivering a capacity of 1527 mAh g−1 at 0.1 A g−1. As found in In-situ Fourier Transform infrared spectra (FTIR), the superlithiation of CTF-2 is mainly contributed by the reversible transfer of electrons in aromatic rings, which results in the reversible variations in the peak intensity during the charge/discharge process. Furthermore, CTF-2 exhibits an admirable cycling stability with the capacity of 1321 mAh g−1 over 500 cycles at 1 A g−1, and a superior rate capability with the capacity of 463 mAh g−1 at 10 A g−1. The prominent electrochemical performance can be owned to the structural stability, porous structures and the rich electrochemical active sites of CTF-2.